The Offshore Voyaging Reference Site

10 Tips I Learned From a Stupid Thing I Did

During the some 35 years that I have owned offshore cruising boats, I have made some deeply stupid maintenance and gear decisions.

That said, I do like to think that I learn from those mistakes and make fewer of them as the years go by. That is, until I screw up again…spectacularly.

This post is about my latest blunder and what I learned from it:

When we hauled Morgan’s Cloud, our aluminum expedition sailboat, last fall, we discovered that the propeller shaft cutless™* bearing had bound onto the shaft and then wound its way a good 8 inches up into the shaft tube. (We have two bearings, the culprit and one in an external strut, which was fine.)

Wait, it gets worse. In the process, the cutless bearing had scored the shaft so badly that a local marine engineer and Lloyds surveyor, who we hired to take a look, condemned it.

I won’t burden you with the gory details of getting the cutless bearing out—if you are a gloating boat-maintenance voyeur you can read them in the posts linked to below—but suffice to say it was less than fun.

OK, I know you’re panting to hear how this turned out to be my fault. Be patient, there’s a story to tell first.

Repetition Sucks

Whenever we have a maintenance disaster, and this surely qualifies as that since it cost us three boat units and more hours than I care to think about to fix, the first thing Phyllis and I do is try to determine exactly what caused the problem so that we can take steps to make as sure as we can that there’s no repeat performance—fixing something once is a pain in the…neck, fixing it twice is a soul crusher.

First Guess

My first guess was that mussel shells had grown between the cutless bearing and the shaft during our winter storage in the water, resulting in the bind up. However, given that I had turned the shaft by hand at least once a week over the period, and we have often spent as long or longer stationary in the water without problems, that explanation never really satisfied, and in fact turned out to be wrong.

#1: If a theory just does not feel right, particularly if you have as much experience as we do, it probably isn’t.

Over the first part of the winter I ruminated…OK, obsessed…about this, before finally deciding that I needed to learn a lot more about the humble cutless bearing.

Crowd Wisdom, Or Not

My first approach was to do some Google searches. But, as I have so often found, the results were disappointing, since I ended up with a lot of crowd “wisdom”, the majority on forums, much of it in conflict, and almost all of it feeling to me like the authors knew less about cutless bearings than I did.

#2: The problem with crowd sourcing is that far more people have an opinion than have real knowledge, and sorting out the two can be challenging.

But I did stumble across a clue: Steve D’Antonio, AAC friend-in-the-comments and all around maintenance guru, has written on cutless bearings in detail and mentioned:

Yet another issue that afflicts some bearings is a swelling phenomenon. At first these scenarios may be mistaken for misalignment between shafts and bearings. However, I’ve encountered several vessels whose bearings inexplicably swelled, causing uniform shaft binding. This scenario can be avoided by using only high quality, name brand bearings such as Johnson Duramax or Exalto.

Could this be the issue?

#3: Zero in on the person who clearly knows what he or she is doing and discard all conflicting information.

Find a Pro

I then broadened my search by looking for a company or boatyard that specializes in running gear repairs and came up with High Seas Yacht Service. One look at their website and technique posts showed that these guys had the specialized knowledge I was looking for.

#4: Often the willingness to share real hard information about their area of expertise is a great indicator that a company or individual really knows what they are doing.

Next I wrote to Chris Brown, principle at High Seas, asking if he would be willing to advise me on a driveline problem for a fee, and also stating that, since he couldn’t actually see the boat or do the work, I was indemnifying him against any liability for the outcome.

#5: If I want help from someone who makes their living rendering that help, I always, always offer up front to pay. Otherwise my email will, quite rightly, be filed under the “just-another-damned-freeloader” file…otherwise known as the trash can.

As so often happens when I’m up front in this way, Chris said that he would be happy to have a quick phone call to help me sort the problem. He also refused payment. I suspect because, even with my assurances, he was worried about potential liability in our blame-oriented world.

I responded with profuse thanks, an offer to call him to save him phone charges, as well as stating that I was in no hurry and that we should only chat when he had time.

#6: If I’m begging for expertise I am very clear that it should be rendered at the expert’s convenience, not mine.

Mystery Solved

Several days later Chris called stating that he was in the middle of a long boring drive and had decided that chatting to me would be more interesting than listening to the Masters golf tournament commentary on the radio—clearly Chris and I have a lot in common.

I told my tale of woe, as succinctly as possible.

As I related the mussel theory, the noncommittal silences were deafening.

After I described the bearing that failed, he confirmed that it was a generic one, probably made in the Far East. And that said bearings swell over time in water, often to the point where they bind onto the shaft and deeply score it (due to heat build up), just as we had experienced—confirmation of what I was already getting suspicious about, thanks to Steve.

Why This is My Fault

So there’s my mistake, and it was a doozy:

I had bought a generic item for a mission-critical application.

In my defence, I didn’t buy this bearing to save money, but rather just because it was the easiest and quickest to source at the time. No matter, the outcome was the same.


How can we avoid this kind of mistake in the future? Here’s what Phyllis and I have resolved. When buying mission-critical parts we will:

  • #7 Take more time and care when sourcing parts like a cutless bearing where failure can really…suck.
  • #8 Whenever possible, buy parts from the manufacturer of the piece of gear in question. No after-market parts.
  • #9 Default to buying parts that are stamped with the maker’s name.
  • #10 Be very careful in selecting the source for a part we buy to make as sure as we can that we’re not getting a counterfeit. For example, we will continue our long term policy of never buying parts over eBay.

By the way, Chris says that at High Seas Yacht Services they only use Johnson Duramax bearings. And guess what? All of the bearings from that company are stamped with the company name and a serial number.

No, it’s not a 100% guarantee of quality, but if a company is willing to put their name, and better still, a batch or serial number on a part, it’s a good indicator.

The Real Mega-Tip

All that’s interesting and useful, but there’s a larger point here. Over the last few years there has been a general trend in consumer society, and particularly around cruising boats, to make saving money a point of honour, to the point of irrationality. Even something to boast about to our friends.

While being frugal is smart, overdoing it is not. This is a dangerous trend that we must guard against, particularly when maintaining an offshore cruising boat. Bottomline, small savings can result in big expenses and ruined cruises.

Or maybe even worse: That generic cutless bearing could have caused the driveline to fail at a critical moment on a lee shore, resulting in loss of our boat, or perhaps even our lives.

And even if we look at the issue purely from a cost basis, the cost of the repair, never mind my time, would pay the difference between good-quality name-brand gear and generic for a lifetime.


OK, you lot, fess-up, what stupid stuff have you done, and what can we all learn from it? Are you man or woman enough to come clean?

Further Reading

Thank You

A big thank you to Chris for taking the time to teach me a bunch about cutless bearings and how they should be installed—might share some of that in a future post, if there’s enough interest (leave a comment).

After talking to Chris, one thing I can tell you for sure is that if Phyllis and I were anywhere near Florida and had any sort of driveline problem, we would beeline it to High Seas Yacht Services to get it fixed by real pros—another way that spending more money up front can save money in the long run.

Yes, that’s the right spelling, at least when dealing with a bearing from Johnson Duramax since it’s their trademark, not cutlass, as one might think.
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Bill Parlatore

Good points about the potential cost of saving money. Glad it had a happy ending.
For your readers who call it a cutlass bearing, here is a short piece I wrote about its creation. Sorry, but don’t see how to make it a hyperlink:

Marc Dacey

Wow, a fascinating bit of industrial lore, there!

John, I like points 5 and 6, particularly. We are having no problems with our newish Aquamet 22 shaft and Thordon Elastomeric shaft bearing, original to the boat. Do you have to be careful of the (usually bronze) metal tube in an aluminum boat because of dissimilar metals?

As for stupid things I do, there’s far too many to list. That’s what my refit blog is for and what my scars attest.


If a reader should find themselves replacing a rudder shaft that turns in a nylon or derlin bearing keep John’s experience in mind.. It is super critical that the dry clearance is sufficient to allow for the swelling that will occur once the part is immersed in water.

Victor Raymond

Very good point. Fortunately I have spares that fastidious owner procured most likely from the Meta yard.

Dan Manchester

For anyone who might want to machine their own bearings I’d suggest the use of Orkot ( as the material to do it – it has a very low level of absorption and expansion and it is what they use in bearings on big ships; it has approvals from ABS, BSI, Lloyds, etc. for exactly that. Avoid the use of Nylon, it absorbs a lot of water and expands considerably.


Hi John,

I’m very interested to hear what you leant about cutless bearings.



Jonathan Caldwell

What a great post! Thanks for your refreshing candor, John. And no, I’m not man enough to list all of my major mistakes, even recent ones, in 40 years of boating. Two fresh ones come to mind where we were extraordinarily lucky in the outcome.

Dick Stevenson

Hi John,
What an impressively scary bullet to dodge.
Too often, I think, we operate with the idea that our motor is a given. I see boats clearing breakwaters (or other gnarley obstacles) by meters where, if they lost propulsion, the boat would be lost in 5 or 10 minutes and lives saved would be a matter of luck. Clearing danger points by a wider margin usually only means minutes lost on a passage, but may allow for sailing out (or running aground on a beach) if things go pear shaped. I often leave my staysail ready to quickly go when wind would allow for reversal of direction if we lost propulsion.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi John and all,
There is the content about which you/ John writes and then there is the possibly obscured message; obscured because we are attending to the important content. I would want to point out that embedded in John’s report is a wonderful template for respectful and clear dealings with anyone in the boat industry.
Following this template, if you will, will certainly not guarantee a good outcome, but I suspect the chances of getting the outcome you want will increase dramatically. The first few sentences between you and who you wish to work with will set the stage for all that follows.
Interestingly, this is an area which the consultant John refers to, Steve D’Antonio, has written about extensively. He was in the industry in the past (boatyard manager) and his present work (in part) is facilitating the best outcome for owners in their relations with boatyards etc. In this way, he can address the relationship from both sides. His web site is a wealth of information and may include some of the writing on this subject. I can try to find if interested.
My best, Dick Stevenson, s/v Alchemy

Chris Phillips

Hi John,

Thanks for sharing. I was recently looking for a rudder bearing and also became aware that swelling of certain materials due to water absorption can be a problem. I became aware of a material called Vesconite, which has some very good properties for machining bearings out of due to its hardness, low friction and hydrophobic properties. In my search for a Vesconite supplier in the US (which I was unable to find) I came across Glide Bearing and Seal Systems who sells material with very similar properties to Vesconite. They call it Glide – 100. I contacted Tim Creighton there, and he graciously offered to send me a scrap for testing, which I offered payment for but would not accept. I ultimately ordered a rudder shoe bearing from him made from the Glide 100 material. Will let you know how it performs over time.

Steven D'Antonio


A nicely written piece, covering a frequently misunderstood subject, and thank you for the nod.

A few years ago I received a note from a representative at Johnson Duramax, who had read an article I’d written on this subject, after which he Google searched my name and “Cutless”. He said he found something over 100 references where I’d used the word (and those were only the ones online). He reminded me, mostly nicely, that the word “Cutless” is trademarked by Johnson Duramax, which means it needs to be used with the ® registered trademark symbol. Clearly it’s been genericized within the trade, so it’s debatable how enforceable this is, however, being the contrarian that I am, rather than add the ® to the articles on my website I simply substituted “shaft bearing” for “Cutless”, and it’s how I always refer to these bearings to this day.

I’m glad you found Chris Brown and High Seas, he and his skilled staff are as good as it gets when it comes to alignment and running gear work (and hydraulics, a division he added a few years ago). So good in fact I dedicated significant space to their operation in an article I wrote about running gear a couple of years ago, it can be accessed here

As a side note, I’m currently cruising in Norway. While walking through a boat yard a few days ago I cam across a vessel whose shaft bearing was made of wood, likely lignum vitae.

Finally, as a consultant, I smiled when I read this comment…

“#5: If I want help from someone who makes their living rendering that help, I always, always offer up front to pay. Otherwise my email will, quite rightly, be filed under the “just-another-damned-freeloader” file…otherwise known as the trash can.”


Hi John,

Great article for the knowledge and also the philosophy.

On our Hallberg Rassy 46 there are a few features I would like you to comment :

It is factory installed with an Aquadrive ™ , if I understand makes things easier for the alignment at the factory then over the years. Is this correct ?

The rudder bearing (and the bow thruster) is equiped with a sort of oil drip, does this needs maintenance ?

Thank s for your advice.

S/Y Hibernia II

Benoit Phelan

Hi John,

Wondering where you get your Aquadrive rebuilt.
You mentioned a shop in Seattle?


Denis Foster

Hello John,

Concerning Aquadrives, can you tell us the signs to look for that indicates a rebuild could be necessary?

The great thing of AAC is that from time to time I go through older posts and repetition of reading brings more knowledge or more precisely I know so little.



Steve D

Regular oil analysis is another good means of keeping track of wear and impending failure. It will also identify water contamination. The analysis is cheap, 25-30 USD, well worth a season test.

Steve D

My profound apologies, I was thinking Sail Drive, since that was a recent topic of discussion. Of course thrust bearings like Aquadrives use grease, not oil.

While there is no definitive way to measure wear that I am aware of, when I inspect vessels equipped with them I conduct two tests. One if the bearing temp under heavy load (about 75% power) for 10 minutes, it should not exceed about 170F. Two, the thrust bushings, those installed between the AD and the support structure that is attached to the hull, should compress, however, not so much that the AD bearing housing contacts the hull-mounted support, frame, bridge etc. The bushings do fail over time.

More on thrust bearings here



This is a most instructive post, but I have to say you have it easy. You have tons of experience and already did most of the hard work on the past.

As a rather new boat owner, even if I try to do the right thing, I end up failing. Take for example a recent failure of the steering chain. A link broke, which stranded me in an unfavourable place.

The prudent thing would have been to replace the whole chain by an appropriate marine grade one, I thought. Well, the offer and support from all those yacht-oriented shops were somewhere between disappointing and clueless.

In the end, the only solution I could find was from a work-shop in the commercial harbour, who pointed me to a shop with spare parts for Caterpillar engines and mobile cranes. With the spares, they fixed the chain for me in a few minutes. Probably not the right way to do things, but it got me going again.

To make things worse, most of the times I’m even at loss what those things are called and which type to look for on the internet. Is the A55 steel type or the one with brass countersnivels the right one? And off the internet, the choice is only between the single one on stock or in some yachtie-catalog and all the rest they can’t get you anyway.

Dick Stevenson

Hi Jo,
Respectfully, I would challenge that you failed. You may have gone down a few dead ends and had to turn around, but I guarantee you, all those who own boats do that. The most important line you wrote reported that you got going again. When you get to your home port you can sort out the details.
One of the more frustrating elements of boats ownership is that there is a learning curve for every repair. I can’t tell you the number of projects I have completed only to want to do it all over again to do it better. Sometimes I do just that.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi Jo,
Another thought, maybe easier in the long run and likely more expensive is to go to the manufacturer. For ex. Edson supplied me with new chain and cables for when I swapped out the old as they knew the specs necessary.
Dick Stevenson, s/v Alchemy



That’s what I’m going to do. Thankfully the companies providing the basics like Edson, Blake, Mercedes, Dickinson etc. all seem still in Business or at least still have someone doing the spare parts.

Matt Marsh

As a general rule, if a design seems to call for a chain, sprocket, bolt, pipe fitting, etc. that can’t be found in the McMaster-Carr catalogue, I prefer to change the design rather than accept the non-standard part. McMaster isn’t necessarily going to be the preferred supplier, but their catalogue is a pretty damn good reference for what’s considered “standard” vs. “non-standard” industrial components.

At some point, someone in the field is going to have to fix the thing, and if he has to spend three weeks tracking down a non-standard part from halfway around the world, he’s going to be cursing for months.


Indeed Matt,
I just had that experience last week. After some more research, it seems I’m lucky an the original part is some industry standard chain. One just has to know that, which is a painful process for me.

Steve D

Actually, the temp I was quoting was for the thrust baring itself, the portion of the AD that absorbs prop thrust, its fwd of the CVs, the CVs shouldn’t be that hot.

Steve D

Yes, sorry, bearing, not baring, and indeed the thrust bearing is aft of the CVs. As it happens, I’m in the midst of editing my book chapter on thrust bearings.

I posted that response after about 30 hrs of travel, I’m in Taiwan now and for the next three weeks (two of those in quarantine).

Steve D

It’s the end of a three year project; it was worth it for the closure.

Worked on the thrust bearing chapter today…

Steven D'Antonio


You took the words out of my mouth, as I was reading Jo’s commentary I thought the very same thing, he figured it out and no doubt learned a few things along the way. Boat systems wisdom is cumulative, it’s acquired, and hopefully retained, over the course of years. It’s true, however, that the more you do, the more you acquire and the faster you acquire it, so that part can be frustrating for boat owners. The two most important elements in this process are a healthy sense of curiosity about how things work, and a willingness to learn.

Tom Service

John – Years ago when I was the Port Captain for a marine construction company in Tampa, I had the benefit of talking with a Johnson-Duramax rep at the Padgett Swan Company, then Tampa’s leading commercial marine shafting and propellet company. It was a common field practice to cool down (freeze and shrink) a propeller shaft bearing with dry ice before inserting it into the tight-fit shaft tube ofva tug or crew boat. The rep taught me that this was exactly the wrong thing to do, and it significantly shortened the life of the bearings. Because the coefficient of elasticity of the bronze shell, synthetic rubber bearing liner, and the glue holding them together are all different, subjecting the bearing to the extreme temperature of dry ice creates a stress across the glue interface which results in separation between the shell and the synthetic rubber early in the life of the bearing. I spent the rest of my time as a Port Captain trying to convince my maintenance guys of this, and probably saved the company some money, but the good ole boys never really bought into my “theory” (which Duramax promulgated as chapter and verse gispel). The greatest temperature advantage that can safely be given a stern tube bearing prior to insertion, and not damage the bearing, is a bucket of ice water. I still hear characters around boatyards touting the benefits of dry ice when installing these mission ctitical elements in a power train.
Tom Service
S/V Tiger Lilly
on the hard at the PSS Shipyard, Chebilang, Thailand
They don’t call it “The Hard” because it’s easy…

Steven D'Antonio

Agreed wholeheartedly re. the dry ice “trick”, I never believed in it, and when I ran into naysayers, I simply pointed to the passage in the Duramax installation instructions which clearly prohibit the use of dry ice (see page 3 ). In all the years I ran yards all I ever did was prep bearings by placing them in a freezer set to +10F.

The fit between the bearing and the strut need only be snug (Johnson refers to it as a “light press fit”), if it requires a great deal of force to drive it in, something is wrong. I’ve placed bearings on a lathe to shave a few thousandths off to achieve the right fit, which again is approved by Johnson. Once installed and held in place with set screws (the bearing shell must be “dimpled” to receive these) the bearing will remain in place barring any issues like those John described in his initial article.

One other practice I developed learning the hard way, always fit the bearing to the the shaft before installing it permanently, I’ve encountered new bearings whose clearance between their ID and shaft OD exceeds the maximum allowable standard. It’s heartbreaking to make this determination after the bearing is installed.

Victor Raymond

So glad Rajah Laut has no “Cutlass” bearing but does have shaft bearings. Not sure what it is called but there is a large out filled tube that the shaft runs through. A thrust bearing is on the tranny side behind a short shaft with two Universals. At the prop end there exists a oil seal, the aft bearing and finally the water seal. Not easy to describe without a drawing but hopefully someone here has seen this design before.

Alan Bradley

This post is worth the price of several years worth of subscription to AAC; like so many others, but this is a great example. Thanks to John and to all the rest who commented. You can never, ever learn enough about working on boats!

David Popken


As always, great information. We just finished a three week cruise from New Orleans to Goodland, FL. Near the end of the trip, I imagined or actually heard a kind of oscillating noise that I thought was coming from the external drive train, i.e. the propeller shaft or shaft bearing. When I put the transmission in neutral, the noise went away. It was not apparent at all rpms and maybe has always been there, because since we recently installed a bimini, engine sounds have altered their tone when under it. The shaft and bearing seemed fine when inspected during the last haul out, about a year ago. One thing that has always seemed odd though, is that the shaft does not free wheel when in neutral and sailing. That could be a function of the Maxprop, but I’ve always wondered if the shaft bearing was a little too snug.

David Popken

Thanks John,

The boat is in Florida along with the engine manual and we are currently back in Texas, but I think the transmission is a JS if that makes any sense. One thing I can attest to is the drivetrain does not exhibit any unwanted vibration. It’s as smooth as silk when running. So, if the bearing or stuffing box is too tight, at least the alignment is seemingly spot on. I have a traditional stuffing box that I monitor for proper flow. All seems good there. Transmission fluid was recently replaced. The old fluid looked as if it had come out of a brand new container instead of my transmission with more than 500 hours on it since the last change. When last hauled, I could turn the prop and shaft by hand, but it was slightly resistant to my efforts. I plan to have the diver check the play in the shaft bearing on the next cleaning, but I think I will leave this on my “nice to do” list for now and take a closer look at the next haulout.

Victor Raymond

Hi Steve,
Thanks for your comment
Maybe SeaTorque has the patent on it now but our sailboat was manufactured in France in the late 80’s and the tube is completely welded into the hull so it must have been a proven system from way back then.

Steven D'Antonio


What you’ve described is,or sounds like, a SeaTorque BOSS or Bolt on Shaft System, made in Florida, a combination thrust bearing and shaft log (the tube that the shaft passes through) system. The log is oil-filled and the shaft is supported within by roller bearings. In addition to absorbing a degree of misalignment using the universal joints, the system also absorbs propeller thrust, while doing away with a stuffing box. They have gained popularity with power boat builders, first being popularized by Fleming Yachts. Fleming began using these from AquaDrives about 8 years ago, but only after Tony Fleming retrofit and tested a set on his own vessel, Venture, for a year.

Steven D'Antonio


No, ST holds no patent on this design as far as I know, they’ve simply popularized it. It’s possible yours was distributed by Vetus, they’ve offered a system like this for many years, which was used by European bilders.

Mike Smith

It’s all been said already, but here’s another angle:

Chuck B

John, thank you for sharing this for the benefit of all. Just today I learned of the “5 Whys” process which can help one to arrive at a root cause:

You’ve already arrived at root cause(s) in this article – I know you’re a root cause kind of guy! – I just found this “5 Whys” description of the process interesting and thought it might be helpful to fellow readers.



Well, My wife Katie and I have only been learning to sail for a year… But I’d say the dumbest things we’ve done so far is trying to launch our 25 foot full keel hunter sailboat on it’s trailer with 30 foot tow strap at the Jubilee rd ramp… Then… stepping our mast while moored in the arm.
There’s also the time the tiller broke off…… Lol, it’s all on video.

It all worked out and we’ve learned alot… We also got 10 footitus and now own a 34 foot boat.



Any thoughts on full shaft tubes? – I was in this marina is South Carolina a few years ago and this marina (who does good engine work, BTW) was advertising full shaft tubes for sportfish type boats. Not sure how much they would add to a slow, low power sailing boat, but wanted to throw the question out to this group as it seemed like an interesting topic related to this discussion.

Victor Raymond

As a lucky owner of full shaft tubes in our sailboat, I can only say that the lack of stress about shaft seals is worth the extra cost. In addition having a true roller bearing has to contribute to a smoother shaft rotation and therefore fuel economy.

The big cost is in original construction. Once that is completed, it is virtually painless to maintain.

Steven D'Antonio

Traditionally, enclosed shafts, particularly on sport fishing vessels, simply involved a shroud or tube of sorts around the shaft. The tube is still flooded with water. This serves two purposes, one, it reduces, to a degree, the Magnus Effect, where the water around the rotating shaft creates drag, as well as disturbing the flow of water into the prop. Two, it prevents fishing lines from getting fouled in the shaft. The drive line still uses conventional shaft bearings and a stuffing box.

The other type of shaft tube is completely different, it is typically oil-filled, the shaft is supported on needle bearings in an oil bath, the oil is retained by lip seals, there are no conventional water-lubricated shaft bearings and no stuffing box. These tubes also typically incorporate a thrust bearing to absorb prop thrust, and universal joints to account for a difference between shaft and engine crankshaft angles.

Denis Foster

Hello Steve and John,

May I ask you what do you think of using mechanics stethoscope listening to mechanical noises ? Either the standard or the electronic versions ?



Victor Raymond

Thank you Steve for the clarification. It is the later, oil filled, variety that we have on our sailboat. I am not sure Joubert invented it but it shows up clearly in the drawings and was not specified as per a particular manufacturer. It is almost exactly as you mention, thrust bearing, oil filled, two universals to align the shaft with the tranny. And of course oil seal, bearing and water in that order at the other.

When we hauled out last week for a quick bottom paint everyone came over to spin the prop as they had not seen one spin so easily before.

James Dylewski

Hi John
I am at odds with a Prop shaft backing out . Here’s the story when I put the boat in reverse the touque actually backs the shaft with enough force to break a bolt I put in the shaft and coupling .I used a 3/8″ grade 5 -8 ,& stainless dosen’t matter in a 1 1/4″ dia. shaft. So I bought a new shaft, cutlass bearing and coupling, keys, the shaft has 2 dimples for set screws .So I aligned the coupling to transmission and added a flexible coupling between them . Launched the boat a 1985 Endeavour 42′ with a Perkins 4-154 and Hurth Tranny. All seemed good till I got to my slip and had lost reverse docked safely and checked .Here is what I found the saft backed up and the PYI (new ) replaced the old one, the key was out the set screws backed out and shaft was as far as it would go being held by the shaft seal . So I never thought that the screws would loosen up in less than 10 min. because I wanted to check the alignment in the water so I didn’t wire seize them . My thoughts are that the engine mounts are wore that the engine is shifting. . I did watch the engine while someone else shifted and couldn’t really see a lot of movement aft or forward. Any Thoughts Help would be appreciated
Thank You
James Dylewski

Steve D

Is it a split coupling (I don’t think it says that)? If so I’m no fan of these for several reasons, primarily because they never go back together the same way, which upsets perpendicularity between shaft CL and coupling face. Some use a clevis pin to lock the shaft to the coupling. By all rights it should be a clevis, roll or taper pin, and not a common fastener.

If the bolt that passes through the shaft and coupling broke it probably means the fit is sloppy, the shaft would have to move in order to get enough “momentum” to break a bolt, especially a grade 5 or 8.

This article on couplings may be useful

James Dylewski

HI John
OK let me clarify my post I’m not a writer I’m a retired Toolmaker. Bought the boat in 1997 and had no trouble, in 2015 I had the rudder rebuilt (Fossfoam) so while the rudder was out I checked the shaft for trueness & solid coupler for fit good slip fit. But it only had one (1) set screw and no dimple . So that is when I drilled the shaft and put a bolt in and dimpled the shaft . Traveled from Erie Pa to Lake Superior 2016 & Trips to North Channel the next 2 yrs. all was good . In 2018 is when the bolt would break and shaft backout the PYI dripless seals stainless collar stopped the shaft . That’s when I started changing different bolt types 5-8 etc. so in my last years trip to North Channel I had a handfull of different bolts and no reverse .This needed fixed this past winter and bought the new Solid Coupler (Buck Algonquin) and new shaft & Johnson cutless bearing. Made sure of good fit and face, this one has 2 set screws. The only thing I didn’t replace are the engine mounts . I have free haulouts at my yacht club (Commodore Perry YC) ,so could it be the mounts? or is there something i am missing. The reason I did not Loctite the new set screws is because i wanted to recheck the alignment after I was in my slip which is less than 300 meters from the lift well, and step my mast so all the weight would be onboard.
James D

Steve D

(John, the PYI is the shaft seal, not shaft coupling.)

The motor mounts should have no effect on the retention of the shaft within the coupling. Most small straight bore couplings rely on twin set screws, if these go into a recess they should be pointed and the shaft drilled with matching pointed recesses, of not drilled then cup-point set screws should be used. The fit between shaft and coupling should be an interference fit, i.e. it should have to be pressed or tapped on using a mallet (never metal to metal, and I do lightly oil all shaft to coupling and shaft to prop interfaces to prevent binding). As noted earlier, a common bolt, even a grade 8, should not be used as a perpendicular locking mechanism, this should be a snugly fitted clevis pin, a taper pin or a roll pin, the key aspect of which is no gap or clearance between pins and coupling/shaft.

James Dylewski

Hi Steve
OK I got it . I will not put a bolt in the new shaft . I will start with tight fit and 2 set screws which the shaft is dimpled for and loctite and wire seize them and go from there.
I’LL post here after shakedown
James D

Steve D

Sounds good. Wish you could share a photo.

James Dylewski

If I am allowed to add photos I will be glad to post them
James D

Ernest E Vogelsinger

James, you can upload your photos to a photo sharing platform (e.g. and add the link here. It is not possible to add pictures (or any other assets) to AAC.

Mark Young

Old thread but a good one.

I have a spare cutless bearing onboard that the previous owner sourced. It is a Caravel brand and says made in Italy.

Does anyone know of this brand is this a high quality bearing ?

I am on the hard and going to replace the cutless as the shaft is out for a polish so this is the time to replace the cutless bearing. It may not need replacing but I will do it anyway – if only to see the process of removing and replacing it so I have the knowledge of how it is done.