The Offshore Voyaging Reference Site

Planning and Budgeting an Engine Rebuild or Replacement

A wiser man than I was once asked what had been the greatest single advance in small craft safety in the last seventy years. His reply was simple and to the point:

The reliable diesel engine.

To which I can only say “Amen”.

So within our refit project plan and budget, the engine fits right at the top of the list. That said, what’s the best and most cost-effective way to guarantee that we fulfill that key requirement ‘reliable’?

An Unreliable Engine Is No Fun

Let’s start from the position that there are few things more depressing in cruising, whatever your horizons, than having to live with an unreliable engine. And, worse still, when you’re a long way from home or help, and the chances of rebuilding or re-engining in, say, Labrador, are slim or none, a dodgy engine could become a serious handicap.

Bear in mind, too, that cost is only part of the equation here, peace of mind is of equal value—that is, being confident that the damn thing will start at the crucial moment.

Rebuild or Re-Power?

Let’s imagine that the boat we have identified as a possible purchase dates from the 80’s, is around 40 feet long, and still has the original engine. It’s working, but has quite a number of hours on it (say 5000), which might certainly be enough to justify a rebuild if it hasn’t had one already. Would we be better to bite the bullet and replace it with a new engine off the shelf, or rebuild it?

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Jukka Aittola

Thank you for this well-written and comprehensive post.

We repowered our 1989 Finngulf 36 last winter following a fairly similar trail of thoughts as written above. The Finngulf 36 is probably a somewhat smaller boat than what was in your mind when writing this text, but I thought that sharing actual recent costs to a 1980s sailboat might be of interest to other readers.

Our boat had a Volvo Penta 2003 with a S120 saildrive and we replaced it with a Volvo Penta D1-30 and a new S130 saildrive. We chose the Volvo for two reasons:

1) the engine room of the Finngulf is fairly small and the D1-30 was known to fit in it without modifications to the boat.
2) we thought that replacing a Volvo with another should be as simple as possible.

In our boat the sound insulation had already been changed and the engine room bilges were reasonably clean so no re-painting was needed. In addition, the components of the exhaust system were considered to be in good shape so we chose not to replace them. The throttle controls and the fuel pre-filter were replaced, and some small changes to the electrical system (a negative bus bar in the engine room) were needed. However, all things considered, the repowering of our boat was probably as simple as one can be.

The price of the D1-30 & S130, including an “autumn discount”, which seems to be offered every year, and a trade-in of the old engine for 1000€, was 8290€ in Finland last autumn. The total price, including the engine, accessories, and about 58 hours of work, ended up being approximately 14400€ including 24% Finnish VAT.

The boat yard thought that the old Volvo 3-blade folding propeller should probably be fine and recommended us to keep it and test the boat with it. It seems now that we may have to change the propeller to a slightly lower pitch next winter, which will add a couple of thousand euros to the final price.

Terence Thatcher

I could use some advice. I have an old 4-108 with many thousands of hours (with newer oil seals) that starts and runs so well that I hesitate to replace it right now. I have owned the boat for 23 years, the engine is 41 years old. (Once I write those numbers, I am shocked by the engine’s reliability.) Further, I don’t trust rebuilds, given friends’ experience. Given my decision to stay with the old diesel right now, would you recommend the Airsep system upgrade? Is there any risk that such an upgrade will accelerate the decline of the engine? My engine space does not suffer from significant oil misting. Is that the only purpose of the Airsep? Thanks.

Philippe Candelier

Our 1995 Dufour 39 has been loaded with a Volvo MD2030, so “only” 29 hp compared to the older 4108 50hp.
The MD2030 aka Perkins M30 can be found in many 34-37’ boats, such as Beneteau Oceanis 351 a boat with a 12000lbs displacement versus 15000lbs on the D39.
A example of the HP inflation.
A friend of mine, just got a 115HP turbo Yanmar on his new Beneteau 49. 115HP. Crazy.

Ernest E Vogelsinger

I recently found an even more extreme example:
Steel boat, 13.5m, 16 metric tonnes. Featuring a 187hp Perkins diesel.
I first thought this would be a typo and asked the broker but he confirmed and shrugged “no idea what the owner was thinking”…

Marc Dacey

16 metric tonnes is our “loaded” weight on a 12 metre steel sailboat…actually, it’s probably never more than 15.5 tonnes. We repowered from a 52 HP Westerbeke to a Beta Marine 60 and cruise at near hull speed in flat water at about 2300 RPM. For economy, we do about six knots at 1900 RPM, so 187 HP seems ridiculous…unless this vessel is owned by someone with a tugboat hobby.

Erik Rudels

Hi Marc,
We are repowering this summer. Swapping an Indenor 60hp for a Beta 60. I still haven’t bought the engine so i would like to ask if you feel you got the power right? We have the exact same specs. Steel, 16 metric tons and 12m waterline. After reading the discussions here I was thinking maybe Beta 50 would do the job!?

Marc Dacey

Sorry, Erik, haven’t checked in for a few days. I would say that depends very much on your cruising area, the percentage of time you motor vs. sail, and rather harder to calculate factors such as your prop size and fuel map, as are discussed elsewhere on this site. We motor primarily when the wind is too light to drive the boat beyond 4 knots SOG or so, or (of course) in restricted waterways. I wanted a 60 HP diesel to have “a little extra” for a second power take-off and/or a larger than usual alternator for our larger-than-customary battery bank’s charging needs, and to still have full thrust when needed for getting out of trouble. This has meant keeping some records of fuel use, RPM at various throttle settings and, last year, the flattening of our prop pitch to raise the RPMs to the desired values. Not everyone is going to have these concerns, but it extends our motoring range by about 100 NM starting with full tanks to be this calculating. Our LOA is 12 metres, by the way, not our LWL, which is considerably less as ours is a full-keeler. I would suggest you factor that aspect of having a (likely) more easily driven hull into account, but were it me, I would like the full 60 HP (actually 56 HP as per the specs) and get a prop to get to the desirable 75% of full throttle (this figure varies somewhat) to get to the most economical fuel usage. The fact that we have a feathering prop, for instance, alone changed the way our diesel worked. because we have four blades. I think if you read more discussion here, you will develop a satisfactory answer to your question. We are, so far, very happy with the Beta 60 for our boat.

William Murdoch

This is timely.

We have a 1988 Yanmar 3HM35F. It was remanufactured by Mack Boring in Union, NJ at about 6,400 hr on 9/2/2010 for $6,131.10. The all up cost was about $10,000 including a local mechanic to remove and reinstall the engine, transportation from NC to NJ and return, new engine mounts, etc. Last year the transmission failed in the Bahamas where it was rebuilt for $4,053.90 to which must be added the marina charges while the work was underway. The repairs were not successful, and the transmission required another rebuild on our return to the US. With an estimate of $5,000 for the second rebuild of the transmission in hand, Beta Marine quoted us $13,221.36 for a complete Beta 30 delivered to NC but not installed. We elected to have the transmission rebuilt by East Coast Marine Transmission in NJ. The actual cost was $3,788.00 including a difficult to locate part and shipping. I did the removal and reinstallation myself. This winter the injection pump began leaking. Its removal, repair, and reinstallation cost $1,708.62. Of course, over the years there have been other more minor costs and headaches associated with the engine. At this point I have a 32 year old engine with 10,979 hr, with decreasing (but still OK) oil pressure, and I am anchored at Hilton Head Island in SC waiting on a replacement engine coolant circulating pump to arrive. My wife points out with some justification that we should have replaced the engine back in 2010. She may be right.

Ernest E Vogelsinger

Anyway, at least at a certain point there should be “no good money after the bad”.
Reminds me on my old Jeep Cherokee, a really fine car but old and having increasing maintenance costs. Last year I decided to throw him out, the financing costs for a comparable new car being only minimal above the costs to keep the Jeep alive. So now I have an almost new car fitting the same purpose, warranted, for only minimal more money but peace of mind.

Matt Marsh

Well, now you have me a little on edge, because I’m in the process of buying something with a 3HM35F in it…. at <4000h, though, which should have a fair bit of life left. I hope.

Transmission rebuilds, it seems, are rarely worthwhile in the smaller sizes. I’d even say that while in-place engine overhauls are probably OK, engine rebuilds that require removing the motor from the boat often seem to result in no real financial benefit over just swapping in a new motor & gear.

Rob Gill

Hi Colin,
With Volvo shaft seals, we replaced ours in 2015 not long after buying our boat, and after 12 years and some 1200 hours – our prop and shaft are locked when sailing. I examined the old seal at the time, and it seemed visibly to be in good condition inside and out, and I have heard of Volvo seals still fine after 5000 hours – like most things on boats, maintenance seems to be the key.
We fitted the new seal and also a second “back-up” seal on the shaft in front of this new one, that just sits there and turns with the shaft.
Five years on, 900 hrs in, and with the Volvo supplied shaft lube regularly applied and with careful “burping” after being out of the water, this one appears also to be in great nick, not even a drop of sea water in the bay. But if it should start to show any sign of cracking or leaking, we can split the old seal with a knife, remove and then slide the back-up seal directly in its place.
I have a feeling this Volvo 500 hours is a “CYA” factor, or perhaps a $$ spares sales tactic, but do you or any members have experience otherwise? I guess there is an insurance risk should the Volvo seal fail whilst the boat is un-attended, but I would be keen to understand the practicalities first.
Thanks, Rob

Philippe Candelier

Actually, the installation manual on the Volvo seal says to be replaced every 5 years and apply grease every 200 hours.
I changed mine that was 8 years old, and it cracked under my hands while burping it.
Using a knife to cut the old one, it very difficult: this is thick rubber, and you need to apply a lot of force. Beware not to create an indentation to the shaft with the knife blade, as this will ruin the new seal Within a few hours.

Petter Mather Simonsen

I exchanged a volvo seal recently and I know when the first one was installed. So my calculation goes as follows; I have a fixed propeller and a continuously rotating shaft. Based on distance sailed and not the engine hours during the period, my guess is that the seal broke after approximately 2,000 hours of shaft rotation.
Greetings, Petter

Stan Honey

If you prefer a lip seal consider the Norscot. It has lip seals that are lubricated with automatic transmission fluid (ATF). There is a sleeve bearing running on the shaft, in the ATF, that keeps the lip seals in alignment. I’ve had good luck with them. It is still recommended to burp them after launching.

Rob Gill

A follow-up comment having replaced our Volvo rubber shaft seal and Beneteau rubber cutlass bearing last week. They are both made of the same nitrile rubber, and have identical bearing surfaces inside.

The shaft seal had done about 600 hours since 2015. We undid the shaft and removed the old seal intact and could see it was in perfect condition with no noticeable wear. It felt exactly like the replacement to the touch.

The cutlass bearing had not been changed from new to my knowledge, so nearly 20 years and was also in really good condition. We replaced it anyway having gone to the trouble to remove it.

Next job to check the engine / shaft alignment.

John Harries

Hi Rob,

Good on you for digging into that stuff, even though all was good. A lot of people neglect the drive line and come to regret it. There is also the insurance aspect of not servicing this stuff at the proscribed interval.

Steven Schapera

I was a farmer for many years, as well as an agricultural contractor. We ran a number of small John Deere tractors with 40hp and 50hp naturally-aspirated, water-cooled Diesel engines. It was not at all unusual to run them to 10,000 hours before a rebuild. Although my Shearwater 45 is powered by a Yanmar, I’ve often thought I’d replace it with a J-D. Having said that, we also ran small Kubota tractors which were whisper-quiet and super smooth but I never owned them long enough to get up to the high hours. It may well be that a diesel that starts off as a tractor engine seems to be built more robustly than one that starts off as a light truck engine?

Rob Gill

Hi Colin,
We have the same trusty d2-55 engine in our Beneteau 473 and doing absolutely everything we can to ensure the engine outlasts us (an ounce of prevention… etc).
But since you have so obviously given this subject some recent careful analysis, if you were forced into an early engine re-fit decision on Pèlerin, on balance would you lean towards:
a) Re-building your existing d2-55 since circa 2008, it is a very simple reliable Perkins marine engine set-up, parts are available and you like/trust the engine?
b) Re-power with the latest model d2-55 since it is still basically a Perkins, you can use the same engine bed unaltered, even though the new models have more electronics and more to go wrong in a marine environment (green death)?
c) Re-power, gear and re-mount/bed with a Beta 50? (50hp @ 2800 RPM)
d) Re-power, gear and re-mount/bed with a Beta 60? (56hp @ 2700 RPM)
And why so, thanks? Rob

Rob Gill

Hi Colin,
Thanks – my thought is I would probably go straight to a new d2-55. The few Volvo mechanics I have met seem to really like them, even the latest versions. And they like working on them, which is often a good indicator of an engine. They remain naturally aspirated and simple, which is a big plus. Not sure about the few extra electronics Volvo has added, but at least they will be new ones!
Anyway, to further extended and protect our exisiting engine’s life, I recently installed a manual “Salt-Away” pump made here in NZ, that I thought you and other members may be interested in. This allows me to inject Salt-Away solution into the raw water system at the end of a trip and on return to our marina berth. We do it any time the engine will be off for any period (say more than four days). The 50% water / Salt Away solution is mixed with sea water in the strainer box, then runs through the raw water system to the exhaust outlet and the engine is shut off leaving this mix in situ.
According to Salt Away, it inhibits salt build-up in the raw water system, breaks-down exisiting salt build up, protects rubber and inhibits metal corrosion. This then protects the heat exchangers, exhaust pipes and elbow, impeller and hot water tank as well as ensuring optimum cooling performance. I have used Salt-Away on my outboards for years and know it works well in that application (even freeing up blocked SW outlets), to restore normal cooling.
And I could tell we were loosing engine heating performance in our HW system last year, but now after three months use we are now close to normal again.
There are alternative chemicals readily available overseas, but having the reservoir and pump makes injecting the right quantity of additive easy, and as a wise sailor has said more than once I believe, “if it’s easy, you will do it”.
Br. Rob

Marcus Petraska

take care with the Beta Marine model designations – they do not equate to hp as we normally know it.

most manufacturers rate their engines against ISO8665 measurements – and if you take a look at Beta engine publications they also provide engine output data to the same standards – but it is usually below the ‘headline’ number.

for instance the Beta ’60’ they declare 56hp @ 2700rpm – but look closely at the power curve and the ISO8665 standard shows only around 46-47hp produced. Beta 50 you mentioned – only 45hp…

you will find this the case across their whole line – the Beta ’90’ is more like 76hp for instance

Alan Sexton

Hi Colin,
I would like to mention that the Yanmars in the power range we are discussing here are also based on industrial engines, the marine JH series is derived from the industrial TN series. Yanmar and Kubota are direct competitors in the industrial segment, marine versions are a tiny proportion of Yanmar’s overall production.
It is possible Steve’s John Deere tractors mentioned above were actually rebadged Yanmars , as Yanmar was OEM supplier to JD for quite a few years.
The “unfortunate” development is that compliance with Tier 4 emissions for both industrial and marine requires Common Rail injection with associated ECU. Yanmar marine released these engines a couple of years ago. Kubota have also introduced CR Tier 4 engines to their industrial line up, continuing to manufacture the older style engines will be a commercial question based upon demand for older style engines.
An anecdote from the installer of my 4JH4 Yanmar a few years ago, he claimed that when Yanmar started development of the JH series back in the early 90’s, they used the 4.108 as their basis. Of course first objective was fixing the oil leaks. True or false, no idea.

John Harries

Hi Alan,

I agree that the basic Yanmars were great engines. I repowered with a basic naturally aspirated one (43 hp if I remember) in my old boat (replaced a 4.107) and it was a great success. That said, then Yanmar started juicing up the base engine with turbo, intercool and on it went. If memory serves, they topped it out at over 100 hp and stuff started to go wrong. Add in common rail, and you have an engine I would not want at any price, at least for cruising remote places. Interesting to note that in 2010 while I was there, Billings Deisel, in Maine, wanted to put one of these in a small lightly used (500 hrs a year) lobster boat and Yanmar absolutely rejected the idea saying “this is not a commercial engine”.

One other point, I think I’m right in saying that the Yanmars have no liners and so I think that may be part of why so many rebuilds of them end badly.

Alan Sexton

Yanmar actually extracted 90kW/125hp out of that 2.0L block in the 4JH3-DTE model. The issue of course is the correct application, those turbo motors were built for light fast planning boats, not heavy sail and motor boats. I agree turbos do not belong in sailing yachts below about 18m . Problem is very few naturally aspirated diesels available now above 65kW/90 hp. If you want a scary number on what is possible consider VW extract 170kW/~215hp from their 2.0L car diesels, using CR and 2 turbo’s!
It is hard to identify which smaller Yanmars have liners, the TN/JH series do, unsure about others. Unsure why they do not rebuild well, maybe it is not possible to replicate the factory tolerances in a rebuild
Steve Dashew in his sailing days looked closely at correctly matching hp to application, his 62′ Deerfoot II ran a 75hp 4.236 Perkins, 84′ Beowulf ran a 170hp LH Yanmar and could motor at 12kts – waterline length is everything.
Nigel Calder has written extensively about engine hp selection (along with props), he wrote with his first Malo 46 that he could not convince Malo that the standard 100hp Yanmar was excessive, he was obviously more successful on the second as that is fitted with a 75hp Volvo.
By the way I consider the Outbound 46 is overpowered with the 75hp turbo Yanmar, I expect you will touch on that in a future review

Steven Schapera

Alan, I believe they were JD as they were manufactured at JD’s facility in Mannheim, Baden-Württemberg, Germany.

William Murdoch

Matt, here is some more of my Yanmar 3HM35F story…

My 3HM35F was rebuilt by Mack Boring when the oil consumption jumped from near none to as much as 1 qt/7 hr. We made a Bahamas trip with it like that burning about 12 gallons of Rotella 15W-40 along the way following the advice of Anchor Marine in Miami — no smoke, quick to start, no expensive noises, just burned oil. We had the engine rebuilt after our return to NC. Mac Boring found the rings in the aftmost, lowest, No. 1 cylinder corroded into their grooves perhaps from salt water ingress through the exhaust. I have since made the exhaust system a bit more robust.

The Bahamas transmission rebuild was first caused by, then failed again, when the nut securing the output flange to the shaft loosened and backed off. During the Bahamas repair, it was not properly tightened with special wrenches which the Bahamas dealer did not own. When it backed off after the rebuild, the ATF spilled, the transmission ran dry, and the internals were damaged. In the Bahamas I cleaned the nut and shaft, wetted the threads with red Loctite and, tightened the nut with a hammer and chisel; the transmission brought us back to North Carolina but with internal damage. That damage was rectified with the second rebuild.

The injection pump rebuild was due to a failed o-rings under the three discharge valve holders. My use of a diesel fuel additive containing butyl cellosolve may have damaged the o-rings.

The coolant circulating pump and its gasket cost me $128.55 delivered to Hilton Head, and I swapped it out myself at anchor. The total time lost was six days.

Some engine parts are “no longer available”. You might want to ask your surveyor directly about that.


Andre Langevin

Nice article Collin and thanks for the information on the lineage of the D2-55, i have a D2-75 on my boat and altough i find many parts in the Perkins OEM market i didn’t know for the Shibaura part.

There is an excellent book by Dave Gerr (that i’m sure you know of) which is absolute reading before starting any repower project: Boat Mechanical Systems Handbook: How to Design, Install, and Recognize Proper Systems in Boats, Dave Gerr. One of the most important rule is not to exceed 1000 rpm shaft speed. As there are not many 4:1 transmission on the light diesel side, that mean trying to find an engine which tops at 3000 rpm and find a 3:1 transmission to mate. There aren’t so many then…

As shaft speed decrease, efficiency increase and also propeller size. All these variables are discussed in Dave Gerr book.

best wishes,

Andre Langevin

Hi Collin,

Dave Gerr goes in great lenght into explaining all the variable about engine size and power vs displacement. Its also there were i found the idea about the North Sea exhaust system, a longitudinal exhaust tube that open on boat side of the boat. I NEVER smell any diesel fume since i’ve owned this boat 🙂

I also with the help of the calculations provided decided to buy a D2-75 where a D2-55 would have been sufficient but turned the extra power into a reduction of cruising RPM to 2000 rpm (less noise, less vibration). Of course the engine is overpropped and it doesn’t make 3000 rpm at full throttle = it is limited to 2700 but his was validated by the Volvo mechanic that did the launch inspection. The engine turns a 24 inch Campbell Sailor 3 blades prop through the 2.8 reduction. When i say no vibration i mean it…

Marc Dacey

I was able to write to Dave Gerr and describe how I wanted to recreate the “transverse North Sea exhaust” in our own sailboat. He was most helpful and made some constructive suggestions. Ours works very well and the main advantages are that the anti-siphon circuit, while still present for insurance purposes, is not superfluous, but also that the exhaust back pressure is significantly reduced. Not every sailing vessel could be adapted to have this setup, but for us, it has been a significant enhancement sparked by Mr. Gerr’s valuable and learned book. A final advantage is the short runs of exhaust hose and the ease of access mean there’s less noise in aft cabins and repairs and maintenance are simply performed. Some further description is here:

Dick Stevenson

Hi Colin,
Very nice report and agree on all points. Having done 2 re-powers and one rebuild, I would go with re-powers any day. Re-builds are way too much dependent on the mechanic and we had gremlins left in ours that plagued us for years: life is way too short…
I support also your suggestion of a wet exhaust overheating alarm. I do not know why they are not standard equipment as they are simple and reliable and can save a world of misery if you do not happen to notice a clog (or other blockage such as operator error not opening the seacock) in your raw water system in time. I notice the URL was for a UK product which may be available in the US and elsewhere. I have used a Borel Raw Water Failure Alarm which seems to function similarly and is well recommended.
My best, Dick Stevenson, s/v Alchemy

Erin Irwin

Well this was very timely for us… Our Cape Dory 36 had a Perkins 4.108 that was blowing a good amount of oil. We had it pulled for a rebuild and had a very good mechanic tell us pretty much the exact story you have written regarding a rebuild and the value of a new engine. The new Beta 38 is literally being mounted this week!

We did pay the price for a new transmission last year, though we were able to resell it to recoup costs.

The new panel is NMEA so it can integrate into our Furuno system, the high output Balmar alternator, the Racor fuel filtering, the new Sounddown insulation in the engine compartment, along with the opportunity to get to all the cutlass bearing area that we noted was a bit “soft” when we replaced the prop with a MaxProp last year- all of this just made us very grateful for a good mechanics advice.

We may have some time to think about adding the dripless stuffing box… did not consider that previously. The advice on some of the safety additions, overheating and fire- very good additional thoughts!

All in all- you just made our day in confirming all our decisions!!

Finally a shout out to the Beta Marine people who were so wonderful to work with. They took lots of time to explain how the repower would benefit us as well.

John Harries

Hi Erin,

Sounds like things are working out well.

A note for others: the Beta 38 is simply a Beta 35 with a higher top end RPM of 3600 instead of 2800. The problem is that to reach that higher RPM the prop will probably have to be smaller or finer and therefore the engine will be less efficient at say 2400 RPM, which will be a good cruising setting.

Bottom line, at each point in the Beta product line they have two versions of the same engine, the screamer and the slow turner, I always recommend the slow turning version since in most all cases with a displacement sailboat the higher RPM settings on the screamer will never be used and because of tip speed and diameter issues with sailboat props, in most cases, the added HP can’t be put into the water.

So, if you really do need more power, the best option is to go up to the next higher HP slow turner in the Beta range, not select the screamer.

To understand all this read:

Eric Klem

Hi Colin,

This is a subject that I unfortunately have a bit of experience with.  I have come to fairly similar conclusions to you and John on what to do.  I now say that for small diesel engines, if you don’t have the skills, tools and time to rebuild yourself, repowering is better than rebuilding.  It is amazing how often there are problems with the rebuild and you still have an engine with many parts that were not rebuilt and are hard to get spares for.  There are a few engines such as the Volvo you mentioned or anything raw water cooled that I would not even rebuild myself.

With regards to cost, the cost of a Beta 35 was $10,500US a few years ago through Beta Marine West and I believe that was without a reverse gear.  I don’t watch prices on this sort of thing but $8k would be a heck of a deal.  $5k to remove and install sounds high for many boats if going the rebuild route but reasonable to good (as implied by your $10k upper end) if doing a repower.  One of the things that I like about Beta is that they will provide custom engine mounts at reasonable prices, these can be very expensive to pay a mechanic to try to figure out.  Bracketing the spectrum a little on labor on the low end, I did a like for like swap with 1 other person in a powerboat with decent access in under 24 hours, it was a commercial boat and came in midday with passengers and left midday the next day with passengers.  I also did a like for like swap on a sailboat in a weekend working mostly solo.  I started saturday morning, had the engine out by noon, then over to my shop and all the accessories moved over to the new long block by dinner, crummy paint job after dinner, started install Sunday morning and it was running, aligned and tested in time for dinner on Sunday.  On the other end of the spectrum, one of the boats I worked on must have had $10k+ parts and labor on just the new exhaust.  I can think of one where the old engine removal was probably 4 man hours and the new install was probably 150 man hours by the time it was done but that was a slightly larger setup than you would find in most cruising boats but still not wildly different and I am not including the furniture disassembly and re installation, I stay away from that when I can.

One thing that often strikes me is that people feel the need to rebuild an engine because it has a certain number of hours on it and I find this to be counterproductive.  Rebuilding an engine is about getting your cylinders to seal properly again, replace worn bearings and hopefully fix all those pesky oil leaks.  However, if the engine starts and runs well with clean exhaust and has good oil pressure, the chances of a catastrophic failure that forces an immediate rebuild or repower are pretty low, the engine will usually show signs first but you do need to be vigilant on checks so that you don’t run the engine for 10 hours with a blown headgasket.  And by doing that rebuild, you take a decent risk that there will be problems coming from the rebuild.  In truth, most of the engine problems that people have as engines get older are not related to the internals that get touched during a rebuild but the accessories which are often left alone during that rebuild.  What can make a lot of sense is to go through the accessories to a high hour engine that is otherwise running well.  This can be everything from hoses to water pumps to wiring, etc.  Generally these are more reasonable for an owner to do, there is less chance of an incredibly expensive mistake and it results in a much more reliable setup.


Eric Klem

Hi Colin,

You are absolutely correct that repowering should be done at the end of the season when possible.  After all, you usually know it is coming for a while beforehand based on how much oil you are buying or how long the engine is cranking when starting.  I have done it this way a few times and it is definitely the way to go.  As my stories attest, I have unfortunately done it midseason a few times too.  In each case, some form of hydrolock was the culprit.  In the sailboat I mentioned, a hydrolock blew the headgasket and since it was raw water cooled, put seawater in the bottom end so it was much easier to find a used longblock from a different application that could be swapped that weekend than get a rebuild kit together and go through the bottom and top ends.

I would guess that exhaust issues are the number 1 culprit leading to mid season engine replacements.  With the boats I worked on, the engines were often so far underwater that exhaust design was a huge challenge.  You couldn’t do a waterlift right off the engine as you would be lifting water 10’+ which means lots of backpressure and huge required muffler volume.  That left running dry, running dry for a while then running a waterlift or a water jacketed exhaust.  I can say from experience that water jacketed exhausts are either unbelievably expensive or unreliable with catastrophic results.


John Harries

Hi Eric,

Good point on exhausts, I bet you are right that they are by far the biggest cause of catastrophic engine issues.

And I agree about water jacketed exhausts. We had one for the first 15 years on MC. Never caused problems, although I did have to replace it once, which was a huge hassle, and I always worried that it would fail a and wreck the engine.

When we repowered we changed to a separation system where the water is first injected at at the elbow to cool the gasses and then separated with the water flowing out of a seacock and the now dry and cool gas exiting out the stern. The benefits are many, most notably very low back pressure, which is otherwise hard to do on a centre cockpit boat. We also raised the injection point above the waterline, so a water lock is much less likely, although that does require about 3′ of dry exhaust. The system has now worked well for 2200 hours.

We sourced it from: Halyard in the UK

They also provided the design customized for our boat.

Marc Dacey

I have been often able to benefit from the “real world” costs listed by others, and as I have done two rebuilds and a repower, I will list them here. All figures are in Canadian dollars, which for ease of conversion can be estimated at 85% of U.S. dollar figures.

Two rebuilds were of Atomic 4s, and each cost about $1,200. I sold one of them for $600. I did all the disassembly and reassembly, removal and installation myself.

I had a 1988 Westerbeke 52 in our current boat with a suspiciously low 1200 hours on it when I bought our present pilothouse motorsailer in steel in 2006. Waiting cerrtainty, and not faith, I obtained a price of $13,000 for a full rebuild. I was able to get a price of $11,500 for a brand new Beta 60 engine with a hydraulic transmission, soft mounts (important on a metal boat), a double power take-off and a few other desirable options. So a repower made more sense and we remain very happy with the Beta engine and, particularly, the price of consumables and spares, which have not only Kubota “tractor” options at lower prices, but even third-party options of high quality from places such as auto-parts stores.

However, extra costs included new engine stringers fabricated in steel for $1500, a new four-bladed Variprop for $4,500, an AquaDrive coupler for $1,700, a thrust yoke fabrication for that for $1,000, a PSS shaft seal for $300, an Aquamet 22 shaft for $700, a Racor fuel polishing system for about $1,500.

I, with the help of friends, did the removal of the old engine and the installation of the new one, which involved removing the roof of the pilothouse, the use of a small crane, and the design and construction by myself of an engine gantry capable of raising and lowering the diesel until we could obtain ideal alignment. So far, so good, but our boat is amenable (with the roof off!) to this sort of DIY approach. Had we a more typical “under the companionway stairs” engine bay, I would have been far less eager to take the job on.

Hundreds of hours of labour went into this job, but I have confidence in the installation to a degree beyond that of contracting out the job to others might inspire. Because, even in a sailboat, the diesel is so key to safe operation and amenities a well-sized alternator can power, I wanted the experience of installing ours to better grasp how to best service and maintain ours, because where we are planning to go as soon as this lockdown is lifted may not always have a mechanic nearby.

Marc Dacey

My intention was to amplify your points, Colin, but I would add that part of my motivation was due to the lack of a maintenance schedule with the old engine, which in a boat of this type should have had more hours on it, or so I would think, and I didn’t have a record of the 18 years of winterizations the previous owner did, a rather important aspect of boating in central Canada. I also took the repower opportunity to educate myself as much as I could about the new engine in particular and diesels in general. So it was a challenge, but also a necessary educational opportunity.

Roger Potts

Hi Marc,I am planning on a repower with the Beta 60. The price you have quoted is exceptional. Was this a bobtail engine and what year did you buy it? I am speaking with Beta in B.C and they are quoting $19,039…….a considerable difference! The bobtail price is $16,433.What transmission did you install? I am in Hamilton by the way! Many thanks, Roger Potts

Peter Ekstrom

Very much agree with the advice presented here. A few other things to consider 1. Very few repowers will happen without some work done to the engine beds, ie building them up or cutting them down, this can turn into a very big part of the project, and its not often done correctly. Big difference between what going on with those motor mounts and beds gliding around the harbor on a sunny day, and putting the spreaders in the water during a knockdown. 2. Front brackets. scope out how your existing accessories – alternators, refrigeration etc will mount on the new motor. New Brackets?, Custom Fabricated Brackets? Both these areas often require skilled fabricators, and the tab can climb like a rocket.

Philip Wilkie

The best advice I was ever given about engines is really simple, pay full attention to all the fluids involved and the engine will rarely let you down. Here’s the mental check list I work to:

Fuel. Dual filters, polishing system and a magnetic bug killer. You must be able to swap out a blocked filter at sea in less than a minute.

Oil. Keep it clean, consider a remote filter if the one on the engine is hard to change. Two forms of pressure monitoring. Consider a simple oil analysis once a year or so.

Cooling. Anodes, pump impellers, desalting, heat exchangers and hoses all need regular attention. Anti-syphon loop location and operation.

Intake Air. Keep it cool and clean.

Exhaust. Minimise back pressure, and do everything in your power to make back flooding impossible. Consider pressure testing to check for leaks, CO is an insidious bastard of a gas.

All of these relate to the engine ancillaries, none of them demand anything other than ordinary mechanical skills. But I’d assert that if you get all of these right, you will have eliminated 95% of the problems that might occur on an engine that was properly installed in the first place. (Assuming other external mechanical items like the mounts and shaft were done correctly.)

We have a 1980’s Yanmar 3QM30 raw water cooled engine. It should have died a decade ago, but all it’s owners have looked after it well enough that the only major repair required has been a total rebuild of the exhaust manifold exchanger. It’s a typical old tractor engine, 350kg of block to produce a miserable 30HP of power and a 2.1:1 gearbox running an 18″ fixed three blade prop. I’ve never taken it above 1800 rpm … big slow props rule.

Marc Dacey

I agree with this assessment. I’ve had to do a kerosene flush more than once due to a failed spring in the antu-siphon (why I hate the things) and had to fish out plastic bags from the raw water circuit (why I have pre-impeller filters now). The “ancillary” parts are actually critical to the steady operation and if you ignore them, you’ll find out why. And yes to big slow props, but it’s nice when they also feather!

Philip Wilkie

A chance conversation with my mechanical guru revealed that the old QM gearbox rotates in the opposite direction to most props. So I’ve put off investing in a feathering prop if and until I ever change the engine.

Then I also found out that I have a somewhat oversized 1 1/2 ” prop shaft that limits my selection of affordable props available in the correct power range.

Erin Irwin

The Beta 38 was the result of long, extensive discussion with Beta Marine and MaxProp. The 38 was their recommendation after of their review of our prop pitch, displacement etc… They reported that they would not sell us a bigger engine- but were very confident in the 38 v 35 for our boat.

John Harries

Hi Erin,

That’s interesting, they are smart people. I can certainly see not going up a size, way too much for your boat. That said, I still wonder if you will ever, in practice, use the RPM range between 2800 and 3600 to get that extra three HP. My guess is that you will pretty much never run it over 2400. Anyway, I would be very interested to hear from you on that once you have had a chance to use it.

The good news is that, if I’m right, you can basically turn your 38 into a near-35 by over-propping it to bring WOT down to say 3200 which will, in turn, make it a lot more efficient and increase your speed (same thing said a different way) at 2400.

Kevin MacDonald

The easiest way to tell how many HP your boat needs is by fuel consumption. 19 HP/gal for a turbo engine and 18 HP/gal NA engine.

Don’t waste your time rebuilding a gear (although it is very easy to do if you have a press), just buy a new one.

Kevin MacDonald

The above is fuel consumption per hour. So if you have a NA engine and burn 2 gallons per hour you are using 36 HP. My 35′ Bristol with a new Kubota D1105, 25 HP@3000 rpm will push me to 7+ kts. That’s a 16,000 lb boat. At a 5.5 kt cruise it burns about 0.65 gal/hr and uses 11.7 HP.

Robert McArthur

We looked at replacing our two Perkins M135 naturally aspirated diesels, max RPM 2600 but we de-rate to max at 2400. With only 3000 or so hours, and purring along beautifully, we were fortunate to listen to some mechanics who said we were mad to change them! I cannot see how to get them out without cutting the aluminium engine room ceiling and then re-welding – eek!
Instead, we’re going to concentrate on adding a parallel hybrid electric motor to each prop shaft after the Perkins+Hurth gearbox.

Robert McArthur

Thanks Colin. We’re still in planning, which covid19 makes easier than doing! We will do our own rather than working with one of the big players such as Oceanvolt. All the discussions we have had with existing players aren’t interested in hybrids on existing engines – they want to do everything. Even Hybrid Marine, who do the parallel hybrid in the Betas, weren’t interested unless we bought a Beta as they had “enough work to do” without getting paid for consulting and one-offs. We have a blog called on which we will put things as we move on (hope that’s ok to write, John?).

John Harries

Hi Robert,

Before you spend the bucks on this, you might want to read this:

We also have a handy dandy calculator that will tell you what the benefits, if any, of this will be. (Thanks to engineer Eric Klem):

Depending on your usage profile, the above two links could save you a lot of money and disappointment.

Denis Foster


Our Hallberg Rassy 46 (16metric tons) is factory equipped with the lowest level of HP Yanmar 4LHTE (110hp) and a Gori prop. This is a 4Liter turbo diesel. I don t know what engine base was used. But a naturally aspirated version has never been available. It seems to be a very sturdy enginethe weak point is probably the turbo (New at2000h) and exhaust elbow (now cast SS).

Like Dashew 62 feet Deerfoot what engine would be used to repower if one day needed. Some HR46 that had the Volvo D3 100Hp repower wit a D2 75Hp.

Thanks fpr sharing your wisdom and knowledge.


John Harries

Hi Denis,

Yes, if you ever do decide to repower you could easily go down to 75hp. Our boat is substantially bigger and heavier than the 46 and we went from 120 hp to 85 with huge benefits and no downsides. In fact I think you would be just fine with a Beta 60 and OK with a 50.

Steven Schapera

My Shearwater 45 has a design displacement if 12,500kg; by the time it’s loaded up for a voyage it’s around 14-14,500kg. It’s powered with a Yanmar naturally aspirated 4JH2E of 50hp, pushing a fixed blade RADICE 17×10 RH E13. It seems a perfect match and I’ve never felt I needed more power. Not sure if that helps anyone here!

Michael Albert

Hi John-
I have to disagree with your unilateral recommendation for feather props. For reference I’ve had a flexofold 3 blade on my boat for 5+ years. I find reverse perfectly adequate- I’ve learned to give it some throttle and it stops my boat just fine. And, I find I can steer in reverse just fine with minor prop walk.
now for the benefits: less drag under sail; less maintenance and simpler/more robust; 1/2 the cost; better performance in forward; and less chance of snagging lines/nets/logs under sail.
As I see it, I spend >99% of my underway time in forward gear or sailing, and <1% in reverse. A well designed folding prop is better hence 99% of the time 🙂

Michael Albert

Whoops, missed edits- feathering props, not feather props. And, I had a variprop on my old boat which was brisker in reverse, but not so much that I think it’s a big deal

John Harries

Hi Michael,

I guess it depends on how you look at it. Your folding prop is a bit less drag when sailing, and as you say, may be a bit better in forward, although I would want to see testing. So you can certainly say “better 99% of the time”. But I see it differently. Being in reverse may only be 1% of the time, but not having enough thrust in reverse when you really need it can be the cause of a disaster. The point being that the fundamental design of a folder means there is always a risk that the blades won’t fully deploy in hard reverse.

That said, I agree that Flexofold and others have advanced the design of folding props a long way in recent years. Looks like some interesting stuff on their web site which I will have a read through.

Also I see prop walk as a benefit, not a drawback. See our coming alongside book for more on that.

These things are all tradeoffs, but having used both prop types I feel more secure about my ability to get in and out of a tight manoeuvring situation with my MaxProp, mostly because in some 35 years of using them it has never let me down, and I tend to put reliability ahead of most everything else.

John Harries

Hi again Michael,

I just read the excellent analysis by Yachting Monthly and it seems that the trade offs are as I suspected: Flexofold: a bit better in forward, MaxProp: better in reverse and absolutely reliable transition from forward to reverse. The other benefit of MaxProp is the ability to change pitch in the field, which is not doable with Flexofold. I see this a big win since getting the pitch exactly right (often a bit over propped) is a huge efficiency gain that will far outweigh any others from blade shape.

So, as usual around this stuff, it’s not a case of better, but rather what benefit each of us values most.

Michael Albert

Great points of course, and I was being a bit opinionated based on my experience :)- and yes the YW analysis is what I was going on. Agree that you need reverse when you really need it. My real world experience is that the flexofold has never let me down, and stops me well enough. The key is to be liberal with the throttle. and it will never reverse like a featherer. Sailing in crab pot ridden waters it’s nice to know a line should slide right past the prop.
I forgot about the ability to change pitch and that is the big advantage to feathering props- and I did that a lot to tweak perfectly with my variprop on my old sailboat.
With flexofold, you can’t tweak. Though, a second set of blades (~1K) is about 50% of the cost of the whole thing (~2K) and are easily changed, so even if the calculations are wrong and you must purchase another set of blades, it still is cheaper. I luckily hit the nail on the head with just enough overpropping on my awesome new Beta 50 coupled with my EGT to monitor load.

One question about the EGT- (and maybe I should post back in the engine mapping thread?)- do you think that correlates most closely with fuel burn? Ie load at given RPM can vary so using RPM to estimate GPH is pretty imprecise. Is the thought that fuel burn at 500 deg EGT is the same regardless of RPM, more or less?


Eric Klem

Hi Mike,

EGT on its own is not a good indicator of fuel burn.  Coupled with rpm information, it can indeed be used but you have to figure out what the mapping is which isn’t trivial.  Think about driving in your car at one speed and choosing between 2 gears, 1 of which yields 1000rpm and one which yields 2000rpm.  The difference in injection events per cylinder each minute is 500 vs 1000 (assuming 4 stroke).  Therefore (ignoring efficiency differences which are there but not huge), at 2000rpm, each injection event only requires half the energy output meaning that only half the fuel will be injected but still the same amount of air. This means that your EGT will be lower despite putting out the same amount of power.  There are several efficiencies that are affected by rpm including volumetric, combustion and mechanical so the actual numbers are not easy to predict.

FYI, if you have a newer common rail engine, the most accurate way to get fuel burn is from the engine’s computer.  How you do this is brand specific but the injectors are so precise these days that it is pretty accurate.  Of course, a flowmeter would be more accurate still but that is an extra component.


Michael Albert

Thanks Eric- helpful to know I’m not missing a trick. And I find the fuel burn curve from the engine is only useful as a rough estimate.
When I repowered, was deciding between Yanmar 4JH45/57 and Beta 43/50. The cool computer data is one benefit of the CR diesels but it was an easy choice for me to go with the simpler Beta once I started learning more about all the ways I would not be able to troubleshoot a CR on my own.
Chartered a boat 18 months ago with a 4JH45, and have owned VWs with CR diesels. Very smooth and quiet. The charter base mechanic told me he didn’t love the CR diesels- had some lightning strikes and other failures take out ECUs apparently.

Michael Lambert

+1 for flexifold, I once got my auto prop caught on two separate pots close to a lee shore(in light wind). That convinced be to switch to folding. It was my second year with the boat(Sabre 362), so hadn’t considered yet that the auto prop was off, but after the switch I got an extra full knot at 2000 I think it was. Haven’t caught lines since, and stopping only slightly slower and I quickly learned the new physics.

Alan Sexton

+1 for geared folders, I have been running a 3 blade SPW Varifold since I re-engined my yacht. Excellent performance ahead and astern.
The Varifolds and the Flexofolds are very similar performers, I looked at both and the Varifold won the day because at time of purchase (2005) Flexofold only offered even number diameters whilst I needed an odd number 21″ which Varifold were able to provide.
Re the YW test one key piece of data missing was a table of RPM, showing whether the props were actually the correct size allowing the engine to achieve full revs. This has always been an issue with Prop comparison tests.

John Harries

Hi Alan,

Good point on the RPM test, and even if they did one they could not have been sure the prop was correctly matched since the engine could have reached max governor RPM before a under wheeled prop fully loaded it.

Johannes Els

Dear John or Colin,
Thank you for yet again a very informative article.
We are 1 season away of repowering our Australian built Bluewater 400

LOA 40Ft
LWL 35Ft
Beam 13Ft
Draft 6.2
Displacement (Lightship) 27 000lb (About 35000Lb cruise ready)
Integral keel, skeq hung rudder, shaft is sightly off centre on port side and and maybe 10 degrees off horizontal, the prop is not sitting in an aperture but it sees relatively “clean” water: all in all, a good setup for effective transfer of power I guess.

The current engine is a Nissan SD 25, small truck engine. Bit of a screamer as John would say- 60BHP at 4000rpm (when new, now 20 years old) driving a 2 blade folding prop.
Not the ideal setup for long distance cruising (previous owner who commissioned the boat was a retired racer and coastal cruiser)
We are looking at a New Beta engine (and new prop) for more efficient long distance motoring, as we sadly often have to do on the New South Wales Coast of Australia.
The hull is easily driven and she sails like a witch despite significant displacement.
My question is would the Beta 35Hp be adequate?
Rather than the Beta 43Hp that the local agent suggests?
There is a sizeable price, but more importantly a 80Kg weight difference. I’m planning to do most of the work myself so I’m obviously leaning towards the lighter 35Hp.
The cost difference is of less influence on such a critical bit of gear.
(will be running a 120A alternator through Balmar external regulator as well)
Would the 35Hp be adequate power??
Your thoughts would be very much appreciated.
Best wishes

John Harries

Hi Hans,

I think the 35hp might be marginal, particularly with that alternator, which will draw about 4hp. The boats Colin was recommending the 35 for are a lot smaller and lighter than yours.

Probably better to go up to the 43, I think. That said, do keep in mind that my recommendation is based on a couple of minutes thought and very little information about your boat. If you want to do this right, get hold of a copy of Dave Gerr’s propeller hand book, which will let you calculate what each engine will really put into the water through whatever prop you decide to select.

Johannes Els

Dear John
Thanks for confirming what I sensed was the right size engine for your boat.
Such an important decision.
Thanks also to Rob regarding the Balmar soft start and over ride- have to admit that I’ve programmed in the sort start but don’t have smart controller interface to turn off the alternator at will. Maybe a bridge to far for me- by the time the engine is fired up I would like to know that I’d be able to motor and charge batteries without over powering the engine.
Best wishes

Rob Gill

With the Balmar external regulator, could you program in a quick soft-switch override for the alternator?
We have a 55HP Volvo for a 47 foot boat but of similar tonnage to yours. We have a 130A alternator from Master-volt, and can turn it off using the smart controller interface – this translates to about an extra 5hp (10%) and you can hear the engine really pick up when we turn the alternator off, if we are really pushing it upwind into a blow and waves.

David Short

This comment is a little off topic but the only thread on props, that I found, is old w/o a comment space. John comments, in this thread, that folding props suck in reverse. I installed a 3 blade Flexofold on my Sabre 362 last year and have found its reverse no different, that I can identify, than the Autoprop it replaced.
However, the more interesting story is the Autoprop. My first season with this 1997 shoal draft boat was 2016 & right off the bat I had a severe “weather helm” problem. No matter the conditions, even in light winds. I went through the whole list; mast rake, adjusted backstay tension, halyard tension, traveller settings, etc. All with the help of my sailing buddy whole has forgotten more about sail trim than I will ever know. The rig was checked over by professional riggers. I grew suspicious of the prop which is an absolute animal in forward and reverse but when sailing, shaft locked or free, seemed to be throwing turbulence on the semi balanced spade rudder causing it to twitch. I greased the prop annually & the blades pivoted freely. No apparent damage or out of balance.
Spring 2019 I replaced it with the 3 blade Flexofold, same 16″ diameter. This is a completely new boat. The helm is light. Previously, in no conditions, could I take my hands off the wheel. Now she balances.
A friend has an Autoprop on his Island Packet 320, on which I have sailed, no problem. The IP rudder stock is offset a little bit, attached at the bottom.
I do wonder if the Autoprop was too big because, approaching a dock, I could not idle the engine w/o it lugging. As said, it was great motoring.

John Harries

Hi David,

I really have no idea, but given that getting rid of the autoprop was the only thing you changed it does seem to be the culprit. I wonder if there was something wrong with that particular autoprop that prevented it from properly feathering, even though you maintained it properly.

Rich Morrow

Over recent years I have had some problems with the Yanmar that was originally installed in my boat (Yanmar 50hp, 1994 model year, first put to the test in 1997 and for many years a great engine). I’m not sure what the origins of the problems were, bad fuel along the way (?), who knows, but it became obvious that cylinder number 4 was only firing intermittently. Rebuilt injectors didn’t help and the problem was traced to the high pressure fuel pump – minimal squirt to number 4. It would be big money to rebuild the pump alone, no easy access to the pump (low on the side of the engine block) without lifting the engine off its mounts etc, and still old everything else to deal with. So, following the key piece of advice in this article I decided to re-power with a new Beta 50 rather than go down the rabbit hole of a rebuild.

As you know, guys working on boats charge huge money and it seems like it’s the same price whether it’s simple wrench work or more specialist stuff, so I did most of the removal job myself. To get the engine out of the narrow main companionway hatch I had to remove the alternator, exhaust manifold, heat exchanger and aft motor mounts. The beast came out end-wise. Guys in the yard lifted it out with their boom truck. To drop the new engine in required removal of the oil pan (known in advance from careful measuring and we had a new gasket on hand) and the engine “feet” were re-installed once the engine had cleared the hatch.

Beta designed and built custom feet for the engine to adjust for the “stepped” engine bearers – (yup about half way back the bearers step up about an inch and a half – I guess because the hull gets narrow quickly back there).

The pros got involved with the installation which was fairly straight forward but not easy in the confined space available. I wanted them to take responsibility for removing and re-installing the oil pan without incurring any warranty issues and for the actual alignment and bolt down of the new engine. They also charged time for the start up and commissioning of the engine, so all in, they billed me for 40 hours of their time (a realistic number given their time and effort on board). I re-attached all the electrics, cooling system and ran new fuel lines. As part of the overall project I also installed a 50 litre day tank that can fill directly from the deck or filled from the big keel tank through a Racor. Here is the new engine in place with lots of work left to do.

The other major complication was that I had to customize the exhaust elbow to give the height needed above the waterline and to fit the space available.

I drive through a three bladed 18 inch J-prop, which has been a great unit through the years and still going strong. With the boat hauled for the season I will dial in a fair bit more pitch to take advantage of the substantial incremental torque that the Beta has over the Yanmar and to avoid the risk of over-revving the engine with the propeller pitch set too low. With the current pitch the boat quickly accelerated to well over six knots and could cruise all day at that speed. With more pitch I think an unstrained seven knots plus will be order of the day.

All in a big expense and effort but I think (really hope!) that with reasonable maintenance that I have taken engine worries off the table for the next many years.
(looks like my pictures illustrating these steps didn’t load – but if you are interested let me know.)

John Harries

Hi Rich,

Thanks for sharing the project in such detail. This will be useful to others since it shows the level of commitment it takes to do these things right. Sounds like you have managed this well. Could you share what you think the final price tag will be?

As to photos, see our comment guide lines for how to do that:

Perry Jones

I put a Beta 30 in my boat in 2020. $13,000. About $1400 more than a Beta 25. I didn’t price the Beta 35 but I would expect you are looking at $15,000, not the $8000 estimate in the article.

John Harries

Hi Perry,

Thanks for coming up on that. I think the difference might be location based. Colin was writing from the UK, where the engine is made and so US$8000 seems about right. See this price:

Also he was pricing bobtail since we discuss gears later. Perhaps your price was with some options and a gear?

Anyway, I will add something about location.

Terence Thatcher

Thank you. Very helpful. I am contemplating the replacement of my Perkins 4-108. Always starts, has had seals replaced, but it is 43 years old, has unknown thousands of hours but definitely over 5,000, covers the transom in soot, and things are beginning to break. It produces more power than my Morgan 382 (fully loaded, perhaps 10 to 11 tons displacement) needs, but here is a problem with the smaller Betas you did not mention. The lift pump of the Beta 38 will not suck fuel out of a Morgan’s bilge fuel tank. One owner has had to install a day tank, filled by an electric pump. Another has installed an electric lift pump close to the tank. What the second option does to the engine’s lift pump is an issue, I fear. Plus, it adds electrical complexity to an otherwise simple engine. I assume, but have not yet learned, that a Beta 35 will have the same lift pump problem. The Beta 43 does not have this problem, but it is bigger than I need and surely uses more fuel. A friend with a sistership just installed a Yanmar common rail 45–also, bigger than required, but its fuel efficiency is remarkable. But then he is relying on a computer driven engine, which, given my struggles just with a cell phone, I should probably avoid. I hope you can comment on my choices. Thanks,

John Harries

Hi Terence,

I would suggest emailing Beta for a solution. They are generally very helpful, and I can’t believe that there is not a solution available. Also adding an electric lift pump is no big thing, they are very reliable and not expensive, so you could carry a spare. Also helps with priming the engine.

Terence Thatcher

John and Colin one more question. Beta has told me that their 35 with the size prop that fits in to my aperture (16 x 11 three blade) will get me 6.9 knots at full rpm, 2800. A Beta 43 gets me hull speed (7.4 knots), altho they recommend a prop bigger than I want. (18×10). On the other hand a friend with a sister ship runs a Beta 43 with a 16 x13 prop and gets hull speed at 2700 rpm. I intend to get a max-prop finally, which I assume are less efficient than a standard 3 blade.
Do I need an engine that will push me to hull speed? I would never do that, frankly, and I have never done it with my current engine. Given your views about engine over-sizing and Ted Brewer’s estimates of engine sailboat engine requirements (he designed my boat), it seems as if the smaller 35 would be a good match. And Colin seems to think so in this article. But I don’t want to spend $16K and discover I have under-sized a new engine which I want to use for years to come. Advice? Suggestions? Thanks.

John Harries

Hi Terence,

I really can’t be sure without doing a full on study, but it sounds like Beta already did that for you. If you want to delve deeper the best resource is the Propeller hand book by Dave Gerr.

That said I guess it depends on how much that added half knot means to you in exchange for a larger prop and more fuel burn at cruise, which is a personal decision.

Bottom line, both engines will work fine, I think, so in the end it’s up to you.

One thing that may help is to think about what RPM range you used on the 4-108 and then look at the curves for that engine and figure the horsepower you were actually using for your usage profile. I will bet it’s surprisingly little.

Terence Thatcher

To update your numbers: I was just quoted $15,600 for a Beta 35, including a 15% “discount.” $17,400 for a Beta 43.

Terence Thatcher

Further on Betas. Several owners of sisterships to mine are having fuel lift problems with Beta 35 and 38 models, even using electric pumps. Also, the standard transmission seems to be troublesome. I have never heard anything positive about dealing with Foley Engine, but they sell an updated and rebuilt Perkins 4-108. Have you any information regarding those rebuilt engines? Thank you, as always.

John Harries

Hi Terence,

I’m not a fan of rebuilt small engines. I have seen far too many of them fail way too soon and they generally come with very poor warranties.