As most of our regular readers know, we completed a 10,000 mile, eight month voyage to the Arctic and back on Morgan’s Cloud, our 56-foot McCurdy and Rhodes aluminum cutter in 2011. A voyage that constituted a gruelling test of all the gear on the boat. Here is our report on how the engine and drive-train did:
New Engine, The Proof is in The Voyage
by John HarriesReading Time: 6 minutes
Previous: Perkins M92B, Initial Report Card
- Better Powertrains For Auxiliary Sailboats and Motorboats
- Understanding An Engine Fuel Map
- What Marine Engine Duty Ratings Mean To You
- Propeller Efficiency
- How To Stop Killing Your Engine With Kindness
- How To Select The Best Power and Propeller Settings For Your Engine
- Controllable Pitch Propellers (CPPs)
- Selection Criteria For The New Engine For “Morgan’s Cloud”
- New Engine For “Morgan’s Cloud”—What We Chose
- Engine Installation—The Devil Is In The Details
- Perkins M92B, Initial Report Card
- New Engine, The Proof is in The Voyage
John, What do you see as the advantages/disadvantages of a high torque/low revving engine? It sounds as if one of your reasons was for fuel savings which you are pleased to have accomplished. To what degree do you attribute the fuel savings to the low rev/hi torque engine vs the new engine just being 25% smaller? I am also interested by what you mean when you describe the Perkins as an “industrial” engine? Thanks, Dick Stevenson, s/v Alchemy
The key to the fuel savings is, as I understand it (I’m not an engineer) the torque curve of these engines which matches the drag characteristics of displacement hulls better than that of higher revving lighter engines. More on that here and here. In addition a lower revving engine will generally, all other things being equal, be more efficient than a screamer. Here is a comment from Conny Harlin, who is head of the power-train division of a large engine maker (not Perkins) that explains more about this.
When I say “industrial engine” I referring the fact that the Perkins engines are based on engines designed for industrial use where they will be required to run at or near full load for their entire working lives driving something like a generator or big pump. Marine use, on a displacement boat with a properly sized gear and prop, is much more like industrial use than the intermittent use that many lighter high revving engines are designed for.
These industrial engines are designed to run at high load for at least 10,000 hours before replacement or rebuild, whereas many recreational high revving marine engines will be at the end of their lives in 2000 to 3000 hours.
Dear John, I would like to comment on your statement that parts are readily available by couriers like FedEx. Some parts of the world that may work well, but in many of the countries I have spent time, Customs waylays the delivery and puts complications/expenses in the mix that effectively undermines delivery. Many countries, even 1st world, the best advice, (as absurd as it sounds) for important items, is often to fly out yourself, get the part and return with it in luggage. “Yacht in Transit” usually makes no difference to officials as well. So couriers can and do get the part to the country with speed only to have actual delivery become infuriatingly elusive behind a web of rules, fees, forms and protocols, always in a different language, and usually in a different location from where you are. Dick Stevenson, s/v Alchemy
A really good point. What I was saying, not very clearly I might add, was that Perkins seem to be able to provide pretty much any part quickly via courier if the local distributor does not have it in stock. But, as you say, that does not solve the problem of uncooperative and even corrupt local customs officials in some countries. That is one of the reasons we carry a huge inventory of spare parts. But, when all else fails, going to get the part, as you suggest, may be the best option.
Nice to hear that you guys are happy with your “Perkins” with low rpm /high torque layout. You see what a change in fuel-consumption that makes….I would also like to add that a low rpm engine last longer before it’s time for overhaul due to wear of bearing,bushings,seals.
And the best is “No worries about Turbo”failures!!!
ZF is a German quality brand and have been around in the industry like Perkins.
I do like your engine room,,clean, organized,and a NO bilge “Crap” floating around.
I’m glad that you guys are happy with your investment of power ,,,,Conny, S/Y Crusader
Thanks very much for the kind words and good information of low revving engines and ZF.
(Conny knows what he is talking about because he is the head of the power-train division of a large manufacturing company—not Perkins/Cat, as well as a boat owner)
Your mention that your Perkins has a 24v energize-to-run solenoid switch certainly caught my attention! Let me describe the events of a delivery from hell, or more specifically from San Diego to Costa Rica. The boat was a 54′ sport fisherman powered two brand new MAN V-10’s. Upon arriving at the fuel dock in Cabo for our first 1200 gallon refill, we were unable to get the engines to restart. One engine would start, but as soon as you tried to restart the second the starter draw killed the first. The “yacht’s” tool kit consisted of a couple of rusty Craftsmen socket wrenches, and as it turned out the owner had run out on an outstanding bill in Cabo so no mechanic would touch it. Next morning everything was back to normal, so after scratching our heads we toddled on south. When we shut the engines down at our next stop we were again dead in the water. The background cause probably stemmed from needing to run the engines at too low a RPM for the regulator settings as we were trying to save fuel and make long runs. (the difference between 8 GPH and 80 GPH on a boat of this type is a mere twitch of the wrist!)
Here is the sequence of the problem: The engines will not run unless they are receiving the full 24 volts required to hold the fuel supply solenoids open. The boat had a generator that runs continuously producing 120v. This in turn was set up to charge the house 12 v battery bank through a charger unit and charge the 24v engine bank through a separate charger. Engine mounted alternators also charged the engine battery bank. There was no crossover switch between the house and the engine batteries, as this would have involved a voltage conversion.
In this set up either a deteriorated battery bank or regulator or 24 v charger failure creates a power boat with zero horsepower rather than 2400 hp! We finally ended up disconnecting the house bank, re-jumping it to produce 24 volts, jump starting the engines from it, and getting enough output from the alternators to bring the engine bank up to 24v.
The take away lesson:
If you have an energize to run propulsion engine system, you MUST have a back up energy source capable of independently producing the juice necessary to keep your engine running. If you depend upon an inverter I’d want two installed in parallel ready to switch on immediately, powered from two separate battery banks. If you are sailing to remote and challenging locations either install a generator as the independent energy source or choose an older engine design that can run independently of electricity.
Sounds like a horror story on a way too complicated boat!
While I wish that the Perkins had a energize to stop solenoid running on 12 volts, I don’t really feel that the way the Perkins is set up is that big a threat to reliability. We have a bunch of different ways to make or get 12 volts including the house bank, an independent engine battery, three separate chargers running off the generator and the generator start battery itself. Also if we did not have 12 volts the solenoid would be the least of our problems since we would not be able to turn the starter motor and start the engine—a limitation that applies to most engines out there since the demise of hand cranks. We do carry a spare 12 to 24 volt converter (and a spare solenoid), but I would not wire it in parallel since both the service unit and the spare could be damaged in, say, a lightning strike, and changing the unit is a matter of five minutes (two screws, one plug).
In summary, while I think Perkins made a design error in this area, few things are perfect and I don’t feel that it is a problem that disqualifies the engine.
Sounds like you have adequately thought thru the redundancy problem. Why am I not surprised!
One thing I did find surprising on the MAN installation was how little voltage drop from full charge was required to shut the solenoid.
ps; If you think the sport fisherman was overly complicated you’d love the 112′ Sparkman & Stephens twin engined, active stabilized, triple gen set sailboat I once managed the build for! In fact all boats that try to become floating houses are too complicated, with the possible exception of Steve Davis ‘s designs.
Thanks for the clarifications which, for me, inexorably leads to more questions. Beta and Nanni engines are based on Kubota blocks, some Westerbeke on Mitsubishi blocks. Would you consider them “industrial” engines? The only “built for marine use from scratch” engine that I am aware of is Yanmar (unsure about Volvo, Vetus etc.).
I could see a high revving engine only getting 2-3000 hrs on a boat where there is only 50-150 hrs a year on the clock. Many (or most) sailboats likely fall into this category and they would likely figure they got their money’s worth at 20 to 30 years of use. Those of us who live aboard and go significant distances often clock up 500 and more in hrs. per year. Many (again likely most) have higher revving engines and I do not know any of my cruising friends who believe they will get so few hours out of their engines.
As for fuel economy, I would be very curious as to the actual figures comparing a well set up high revving engine and well set up low revving engine. I suspect it is not all that great for the average displacement sailboat. A conundrum is the fact that basically, lower speeds save fuel dramatically (as measured miles per gal.), but the engine “likes” higher speeds. (My Westerbeke 42B uses approx 0.55 gph to push me 5.0 knots and 0.95 gph gets me 6.0 knots—4500 hrs on eng). I almost never go optimal speed/rpm for the engine (70-80 % of power available if memory serves which would push me approx 6.6 knots) as the fuel usage just shoots up off the charts (mpg drops comenserately). I am not sure how to get around this we all want “reserve” power for emergencies and those times when it is important to pound our way up-current, up-wind and up-swell/wave.
Thanks as always for your thoughts, Dick
I’m really not enough of an expert to get into this level of detail with any authority. But I think the key issue here is just the one you identify: With a high revving engine it is very difficult to load it properly in a sailboat and still have enough power for all conditions. The result is the insanity we often see with say a 75 HP 3600 RPM engine in a 45 foot boat where no more than 40 HP at about 2400 RPM will every be used and the same boat would do a lot better with a 40 HP low revving high torque engine, assuming you could find such a thing these days. (My first draft suggested a Beta, but then I found that their 38 HP revved at 3600 RPM—woops.)
I guess the real bottom line for me is how many commercial vessels or industrial generators do you see driven by high revving screamers? Precious few. In fact Yanmar themselves will not even sell an engine to a commercial lobster boat in Maine. So, yes the weekend sailor that does 150 hours a year will be fine with a screamer, but those of us that put commercial equivalent numbers of hours on our engines might be better served to consider the engines that the pros use.
As for fuel efficiency comparison of two well set up engines, one a screamer the other high torque, I guess I would just defer to Conny Harlin on that one (see the link on my last post).
The bottom line for us is that the Perkins has given us really good fuel consumption at low revs (we can go down to less than a gallon a hour at 6 knots if we must) but will still push MC into a 25 knot breeze with a big chop, it just works for us, and way better than the higher revving Cummins ever did.
I’ve often seen identical block marine engines (including Yanmars) with two different power ratings and service recommendations available from the factory. Often the only difference is the governor settings for RPM, and perhaps the injector pump delivery mapping. So I’m not sure how much difference there really is between a “low speed” and a “high speed” engine in these smaller sizes.
That “yacht rated” 3600 rpm 75 hp engine you mention will in fact produce about 40hp at 2400 rpm. If it were coupled to a controllable pitch propeller like we sometimes use in large sailing vessels it might well run quite comfortably loaded up to work at 2400 rpm and last as long as the same engine rated at 40hp, assuming it has electronic sensor controlled fuel mapping. In order to use the available 75 hp. you need a way to change the propeller loading on the fly.
Choosing a broad torque curve and a simple, non-turbo design like the Perkins gives a long engine life and the widest usable power band that can be absorbed by a fixed pitch prop, even though it might theoretically be outperformed by the set-up I just described.
Great comment, as you say that’s the bottom line. Sure there are other ways to deal with the intrinsic inefficiency of many sailboat power trains—variable pitch props, diesel electric (in theory)—but a low revving engine with a flat torque curve like the Perkins is the simplest and least expensive. And it has the added advantage that low revving engines, all other things being equal, last longer too.
I seem to recall that you changed your prop pitch with the new engine installation. Couldn’t some of the fuel economy and performance be attributed to that change?
As it happens, we did not change the pitch at all. But that is simply coincidence because the new engine was smaller, but the transmission has a slightly higher reduction. See this post for more on how prop pitch affects fuel economy.
I’ve done a couple of AquaDrive installations but have no long term experience with them. What is your bottom line conclusion? Is the cost justified?
I think it depends on the number of hours you do a year. For us, it is well worth it since it enables us to get less vibration and noise with a four cylinder, that is intrinsically unbalanced, than we did with our old six, which is intrinsically balanced and therefore smoother.
Also, I believe it will make the mounts and transmission last longer without service, which will help to offset the cost.
I guess if pressed for a rule of thumb, I would say more than 500 hours a year, its worth it, less than that, not.
Hi John, have had a Perkins like yours in a sail boat. The engine crashed after 12 000 hours by accident. I think they last about 22 000 h i fishingboats before main service. Clean dieseloil without water is important to make them run long and fuel polishing is good.
I put in a Yanmar with a ZF and Aqua drive. The Yanmar is still ok and I hope it will last til 22 ooo hours. The ZF broke down in The Arctric with no wind. A friendly fisherman told me that I used the wrong oil and gave me 5 gallons of SAE 30 single grade oil. ZF told me not to use it but I tried and has now made 8 000 hours on the wrong oil.
Aqua drive needs good alignment! The two shafts can be on different levels, but they must be paralell. It is a common mistake to beleave that they can absorbe everything. I make the alignment at normal speed with warm engine, ca 2000 rpm, off shore. Alingnment can not be done in harbour or ashore. To do this you need laser tools. Fixtur laser has the best tools, but there are many options. My aquadrive has lifetime of 100 000 hours. I was first offered the 3000 h, but denied, got 30 000 h offer, but choose 100 000h. It has now made 20 000 hour without service. It is bigger than yours, but the price is almost the same.
Your shaft seems to small, the bedding to light and the gearbox must be fixed. The bedding should be stiff also sideways, bed weight the same as the engine, but better two times the engine. Then it is quiet. If you have rubber moutings, get them as stiff as possible, but better is to leave the engine direct on the bedding.
In my motorboat the engine runs at 300 rpm and use 150 grams diesel oil pr. hour pr. HP. That is 40% less than your Perkins. It has has no gearbox, the ZF takes about 20% of your energi production. It has now passed 120 000 hours and is expected to do 200 000h before next service. I always heat the engine before start and start the lubrication oil pump before start. So when I start the engine is warm with 3 bar oil pressure. That makes the engine last.
All very interesting. I guess we have different goals: To us the whole point of going with the Aquadrive, which was installed in strict accordance with their instructions using a custom made alignment tool, was to use soft mounts so that we could cut down on noise and vibration.
Yours, sounds like a full on commercial installation, which while great for your needs, may not be practical or cost effective in a sailboat. For example, although a 100,000hr life is impressive, we have only run our engine for 12,000 hr in 26 years (including previous owner). Therefor 100,000hr would take…a couple of hundred years—you get the point. And we probably use more engine time than most sailboats. So, like in all things, our engine is a compromise. We have designed and sized the engine installation for our intended mission and acceptable maintainability at a cost level we can live with.
Hi John, i do not expect to do the 100 000 h, I want the safety of it. The cost is almost the same. If you go to Svalbard, there is no boatyard.
The modern theories of rotating shafts are not well known. But all Nato-ships are very quiet, mostly the subs. When Kongsberg Weapon and Thoshiba published how to make a quiet propeller, all the Nato gouvernmets were angry. Norway had to send the spyship Marjata to the Murmansk fiord to observe the new russian quiet subs. This is why theories of rotation shafts are not known to you and your boatyard. But they are simple and not costly to follow and you can improve your boat a lot. It is the theory of the stright line. Easy physics for an old sailor used to the same maths with his sextant. If you know sinus and tangens, you can do the theoretical part of it.
Sweden is outside Nato and the swedish company Fixturlaser has published how to get a quiet engine and shaft. Some of those principels I have mentioned above. I understand that you do not want to take out your Perkins and do your istallation proper. We call that a comprimis. What risks do you take sailing your way: water leaks in the through hull fittings, oil leak in the gearbox, oil leaks between gearbox and engine, and bearings in the aqua drive break down. But with a good sailboat that is not important to many.
I have with a friend adjusted many sailboat engines like yours without doing any rebuilding. We use laser tools offshore. We try to find the best possible solution of the problem within the ecsisting frames. Often we just do small adjustments like lifting the front end of the engine something like 2mm. The normal result is: 30% noice and vibration reduction, 10 -20% reduction in oil consumption. Lifetime of the bearings increased almost to the normal 30 years. If you say you dont like the cost of this, I will do it for free to you in Norway.
Aquadrive is an offspinn from the car industry. Car parts are much cheaper than marine parts. I buy aquadrive parts by Kardang aksel in Oslo to a fair price. You do not have to pay much for that stuff.
All interesting stuff, particularly aligning an engine with a laser. I have always felt that there had to be a better way that feeler gauges.
Maybe we will take you up on it when next in Oslo. We love free!
Hi John, Morgan’s Cloud and crew are very much welcome back to Norway. You just have to cross the fiord. We will fix some laser sensors to your shaft, gearbox and Perkins and then sail off until the engineroom has the normal temperature. Then we do the alignment. We work mostly on The West Coast. The oil industry (drilling platforms, work boats) has lots of rotating shafts with lots of power and speed. They need perfect alignment. Here it is not a question of noise, but to prevent brake downs. Stops are costly.
Last week I was sailing in the Skagerak and reading 3 different pilot books of Norway. I have now ordered yours and will bring it with me on a two week trip in The Barensts Sea, starting next week. I look forward to that.
Best regards and fair winds to you.
Wow, I’ve been reading through your online book on ”Engines for cruising boats”, etc., and the wealth of information is, well, ….overpowering ( yeah, I couldn’t help that one…). But truly, it’s tremendous.
So, to make a long story short, we’re looking at possibly /probably replacing our 23 year old / 2600hr Perkins M80T on our 45′, 18 to 20 tons at full load, steel centerboard prior to departing with the kids on our longterm, part high latitude, life.
I’ve been able to get ”some” idea of where to start but would like the counsel of a pro on selecting the proper engine, transmision, prop, etc, and I want to pay for it! – do you have someone you could recommend?
I know he is very busy with his day job and family, but you might want to see if AAC Engineering Correspondent, Matt Marsh, would be willing to take this on. See http://www.marsh-design.com/content/about-us
Matt wrote all of the really technical stuff in this Online Book.
Thanks for the response – will get in touch with Matt for sure.
While I wait for Matt to have a moment to respond to my email – To get me started, would you have some form of calculation guideline for sizing the appropriate engine that takes into account displacement as well as hull speed, plus the fact that with your latest re-power you still ended up with ”some” glazing – we are not at the moment planning to go to Antarctica, but Patagonia, Greenland and Alaska among others (dreaming big).
Many thanks again for all the info and best regards.
Sorry, I don’t have a calculator that I can point you to, but based on my own experience I would say that our Perkins 87 HP would be a bit big for your boat. If it were me I would be looking at the Beta Marine engines at around 60HP and go for the low rev/bigger displacement option at around that size. These are M2 engines, so you can actually run them at 80-90% power continuously, so the usable power is much higher than a recreational engine like the Yanmar or Nani.
And one of the great things about the Beta is that if you do end up a little overpower, you can over-prop a bit and Beta won’t be upset or cancel your warranty. (I have that directly from the CEO at Beta.)
Emery, if it’s any help, I put in a new Beta Marine 60 in our 16 tonne 42 foot steel pilothouse cutter a couple of years ago, and we are very happy with it to date. I have a 19 x 15 four-bladed Variprop and I can maneuver with authority even with a semi-full keel. They seem to me to be great, strong engines and are easy to service. We installed it with a ZF25 M hydraulic transmission and had custom engine stringers, soft mounts and a thrust bearing for an Aquadrive unit, which I recommend for any metal boat that is re-engining, as (aside from addressing alignment issues) this set-up really reduces vibration and noise.
If you think the 60 isn’t enough, Beta sells a 75 hp today and are introducing a new 70 hp in September that might suit your needs perfectly.
I was having a hard time coming up with HP size, as it would seem to me that displacement as well as hull speed were both important factors to consider as they can vary quite a bit + I’ve been seeing the rule of thumb of 2 to 5 hp per ton depending where you look – not much help that one…
FYI – Beta 60 = 4 cylinder – 2424cc – 56hp max at 2700rpm
Just took a look at Beta’s site. I guess I might consider the 75. Probably more power than you need, but you can always over-wheel it a bit if so.
That said, this is a guess. When spending this kind of cash you really need to get a naval architect to do the numbers since rules of thumb are, as you have found, pretty useless.
If Matt can’t help you on this. Try Ed Joy :https://www.edjoydesign.com
He will be able to sort it for sure. Just make sure he understands you don’t want a M4 or M5 rated engine.
I’ll hang on a little to see if Matt has a little free time for me – Was planning on re-powering in the fall but will probably get a better price if I order sooner rather that latter (new prices coming later this summer)
What are your thoughts on the Autoprop coupled to one of these (60 vs 75) – is it worth the investment vs the performance (light air, etc.) for our boat/hull type?
Thanks again, and again, and again….
Autoprops are interesting and efficient, but I hear there have been reliability issues. The other issue is that if you have a hydraulically activated transmission an Autoprop requires a shaft lock. For these reasons I prefer the Maxprop.
Thank you John,
In the meantime, got in touch with Matt and looking forward to working with him.
Also got in touch with Beta in Vancouver about what they would recommend engine wise and to get the fuel consumption map
– on this last issue, Beta Canada’s answer;
”I have failed to obtain a fuel map, apparently Kubota guard this information closely. The consumption curve that Beta supply is all we can get from Kubota”
Any suggestions ?
I wouldn’t worry too much about getting a full fuel map. A simple consumption/ torque / HP graph is fine for engine selection purposes once you understand the issues and make sure you are not buying a M4 or M5 rated engine.
Read your article with great interest.
Checking the Perkins site it seems they only have the low rev, high torque engine you installed.
Nothing smaller for 40~45 foot boats.
Any other engine manufacturer you are aware of that builds similar?
Yes, that’s right. Perkins no longer sell smaller engines. That said, I believe some of the small Volvos are Perkins engines painted green. A good option for a slower turning simple engine in small sizes is Beta Marine.
Volvo D2 40 which might suit, is based on the Perkins Engine, or the D2 55 – ours has a “Proudly Made by Perkins” plate on the back of the block. Volvo has added more electronic timing and fuel injection controls which our fairly basic 2002 engine didn’t have. You would want to check this out carefully, because the electronics can be problematic on some Volvos I have heard.
Very satisfied with our Volvo/Perkins engine on our 47 foot yacht – reliable, frugal and almost no signs of wear in latest oil change analysis, after nearly 2000 hours.
Thanks John and Rob,
Will look into that. Should even be easier in Europe where I live given the provenance of the manufacturer
I repowered my sailboat with a Kubota D1105. It has a 12 volt energise -to-run solenoid that can be removed and the hole covered with a blocking plate. When the solenoid is energised the plunger retracts and is therefore the same as removing the solenoid. Now, no electric is needed for the engine to run. Of course the manual fuel shutoff lever must now be used to stop the engine. IMHO this is a better, more reliable and fault tolerant setup for a mechanical diesel. I don’t know if there is an energise-to-stop solenoid available for these engines but that is another option if wired to a momentary switch to turn off the engine. I wouldn’t even consider a 24 volt solenoid on a 12 volt boat. There’s nothing to like about that.
I agree, less that ideal. That said it’s been a great engine so far, and we carry spares for the somewhat funky fuel pump and solenoid situation. If I had to do it again I would consider a Beta, but at the time they did not have an engine big enough. Also, the Perkins is even lower revving with better torque. As in most things around boats, it’s all about tradeoffs, not ideals.
There is an energise-to-stop solenoid available for the beta 25 at least. Actually, at least with the panel I have, it is the default. There is a momentary switch that is used to stop the engine.
I learned that there is also a manual stop lever on the engine in case the switch or solenoid fails. The battery negative cable got loose, and it took me a while reading the manual at the middle of the night to figure out how to switch off the engine.
Have been very happy with the small beta, quiet and very reliable.
I think all the marine and industrial diesels are good. It’s all about finding the best fit for the boat it’s going in. Knowing how they work goes a long way in fixing any issues that will arise. There are plenty of ranches and farms in florida that run irrigation pumps with Perkins diesels 24 X 7 for years, only stopping for the long overdue oil changes. They are in a lot of tractors also and parts may be available from the tractor dealers. Massey Ferguson uses or used them it a lot of their tractors. The high revving Yanmars are fine in pleasure sailboats and will most certainly rust out before wearing out. It’s the peripheral equipment that goes bad unless there is serious overheat issues that go unaddressed. If you want more torque, just increase the reduction ratio. (torque multiplier)
Hi John, first, thank you for an amazing resource, it’s been a huge help in so many areas. How did you end up grounding the engine and thus the whole boat with the drive saver installation and have you been satisfied with the results and durability of the ground?
Thanks for the kind words.
She is an aluminium boat, so the engine is not grounded. https://www.morganscloud.com/category/aluminum-boats/care-tips/
With a fibreglass boat it’s easy to connect a piece of copper strapping across the drivesaver.
Ahhh, right. Do you feel the the strapping or brushes are reliable enough? I’ve seen so many electrical issues come down to intermittent / poorly connected grounds, just trying to weigh potential pros and cons of a drive saver. Thanks.
Neither brushes or a strap over the drivesaver provide a reliable connection to the boat’s ground system. The latter because the oil in the gear can insulate the shaft, to at least some extent, from the engine block. My thinking is to leave the shaft isolated and then make sure the shaft and prop are properly protected with anodes. Then the rest of the boat’s metals needs to be protected with an anode and bonding. Point being that a shaft anode should not be relied on to protect all the boat’s immersed metals.
Summary, whether you have a drivesaver or not is irrelevant to the bonding, grounding and corrosion protection system.
And then there is the whole debate about whether or not to bond seacocks…and then there is lighting protection.
Probably your best bet is a good read of ABYC standards, even though I, and others, don’t agree with every single detail, it’s still a great place to start.