10 Tips I Learned From a Stupid Thing I Did

Stupid on the left, smart on the right.

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 Durmax 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.

Like what you just read? Get lots more:

Please Share

Meet the Author


John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

48 comments… add one
  • Bill Parlatore May 24, 2017, 12:33 pm

    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 May 24, 2017, 1:42 pm

      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.

      • John May 25, 2017, 7:55 am

        Hi Mark,

        In metal boats we use a non-metalic cutless bearing.

  • RDE May 24, 2017, 4:02 pm

    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 Jun 1, 2017, 5:25 pm

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

  • Dan Manchester May 25, 2017, 4:36 am

    For anyone who might want to machine their own bearings I’d suggest the use of Orkot (http://www.orkot.com) 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.

  • Bryce May 25, 2017, 6:21 am

    Hi John,

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



  • Jonathan Caldwell May 25, 2017, 9:27 am

    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 May 25, 2017, 11:41 am

    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

    • John May 26, 2017, 6:56 am

      Hi Dick,

      I agree that people are often far too complacent about nasty hard things to leeward and, like you, we have a staysail ready to go, one of the reasons I like having it on a roller furler.

  • Dick Stevenson May 25, 2017, 12:06 pm

    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

    • John May 26, 2017, 7:02 am

      Hi Dick,

      I agree, how we approach people who work in the industry is very important and emphasizing that was much of my agenda with this post.

      When working on our boat I tend to wear Dickies work clothes and so look much like the guys working around the yard in a place like Billings in Maine. On several occasions I have been approached, or perhaps accosted is a better word, by yachties that want something and been appalled by their rudeness.

  • Chris Phillips May 25, 2017, 1:12 pm

    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 May 26, 2017, 8:00 am


    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 http://stevedmarineconsulting.com/wp-content/uploads/2014/03/Shaft-Alignment-159-02.pdf

    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.”

    • John May 27, 2017, 8:20 am

      Hi Steve,

      Glad the piece worked for you, always nice to have confirmation from an expert on the subject. And thanks for the heads-up on the JD trademark, I will add the mark, although I suspect, as you say, that ship has sailed for them due to general usage.

  • Foster May 27, 2017, 2:58 am

    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

    • John May 27, 2017, 8:16 am

      Hi Foster,

      While an Aquadrive makes alignment easier in some ways, that’s not really the prime benefit. Rather the big payoff is that the unit transfers the thrust to the support member the bearing is mounted on instead of said thrust being absorbed by the engine mounts. This, in turn, allows the use of softer mounts, which reduces vibration. The downside is that Aquadrives need to be rebuilt every 2000 hours or so—exact period depends on installation angle and HP.

      As to the rudder and bow thruster, I’m sure some maintenance is required, but I have no idea what that is. I would suggest looking at the manual for each unit. If you don’t have a manual, then contact H&R and get one, as well as the manuals for all of the other kit on the boat. This is a vital step in assuring a reliable boat.

      • Benoit Phelan Nov 9, 2018, 3:00 pm

        Hi John,

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


        • John Nov 10, 2018, 8:56 am

          Hi Ben,

          David Lee
          Drivelines NW, Inc.
          425.258.4013 X3003

  • Jo May 27, 2017, 4:58 pm


    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 May 28, 2017, 3:23 am

      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

    • John May 29, 2017, 7:45 am

      Hi Jo,

      I hear you, this stuff can be truly frustrating, and I do think that it’s in many ways worse than it was when I was learning about maintaining a voyaging boat because back then the profit margins as marine stores supported better qualified staff than they do today.

      On the other hand, I didn’t have the the internet, so you certainly have that advantage.

      Anyway, perhaps I can help with this specific problem:

      A good source for the stainless steel chain that will fit and be correct for most steering systems is McMaster-Carr. Also, most such chain is stamped with a number or “trade size”. Here’s the page:


      • Dick Stevenson May 29, 2017, 9:06 am

        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

        • Jo May 29, 2017, 6:13 pm


          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 May 31, 2017, 7:37 am

        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.

        • Jo May 31, 2017, 6:34 pm

          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.

  • Steven D'Antonio May 28, 2017, 4:05 am


    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 Jun 1, 2017, 8:44 am

    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…

    • John Jun 2, 2017, 8:00 am

      Hi Tom and Steve,

      Good points both. Thank you.

  • Steven D'Antonio Jun 1, 2017, 12:32 pm

    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 http://www.duramaxmarine.com/pdf/FlangedBearingInstallation.pdf ). 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 Jun 1, 2017, 5:38 pm

    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 Jun 1, 2017, 10:23 pm

    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!

    • John Jun 2, 2017, 8:11 am

      Hi Alan,

      Thanks for the kind words, much appreciated.

  • David Popken Jun 1, 2017, 11:08 pm


    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.

    • John Jun 2, 2017, 8:20 am

      Hi David,

      I’m guessing that you have a hydraulically activated transmission. If so, a Maxprop should free wheel unless the engine is stopped in forward gear, in which case it feathers and will then remain stationary. (See the Maxprop manual for more on that.)

      So further assuming that you are not stopping the engine in forward but the Maxprop is still feathering, that does sound as if the shaft is binding for some reason.

      To check, grab the coupling and try and turn it by hand. You should be able to do this reasonably easily without tools. If not, I would investigate further. There are a whole bunch of things that can cause a tight shaft, but poor alignment or a bent shaft are probably the most common.

      • David Popken Jun 2, 2017, 10:53 am

        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 Jun 2, 2017, 4:33 pm

        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 Jun 2, 2017, 3:11 am


    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 Jun 2, 2017, 5:26 pm


    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 Jun 3, 2017, 8:30 pm

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

  • Chuck B Jun 6, 2017, 12:04 am

    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: https://en.wikipedia.org/wiki/5_Whys

    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.


  • Chad Jun 15, 2017, 9:28 pm

    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.


    • John Jun 16, 2017, 8:10 am

      Hi Chad,

      Sounds like you are doing exactly the right thing: getting out there and trying stuff in a smaller boat, learning from the experience, and then going up in size.

  • Tom Jun 20, 2017, 3:07 pm

    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 Jun 20, 2017, 4:09 pm

      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.

      • John Jun 20, 2017, 6:04 pm

        Hi Victor and Tom,

        Although I agree that full shaft tubes have their benefits, they are also MUCH more complex than a simple stuffing box (or dripless seal) and cutless bearing.

        The point being that I’m not at all sure they represent a panacea. In fact the season we were in Svalbard some years ago a meticulously built Dutch boat had one of these full shaft tubes seize solid on them and were faced with dragging the boat up a beach with a D8 Cat to fix it! And then only after several weeks waiting for special parts from Holland at vast expense. Contrast that with a Cutless bearing where we can easily carry a spare for less than $100

        Also, as far as efficiency is concerned, an interesting thing I learned in all of this is that a properly specified and aligned cutless bearing does not touch the shaft. Rather the shaft floats on a thin film of water between the bearing and the shaft. So again, not sure there is any efficiency gain for one over another.

        The point being that like most everything around boats, there are advantages and disadvantages to both approaches and the secret to success and reliability is in the details and quality of installation and parts.

  • Steven D'Antonio Jun 20, 2017, 4:21 pm

    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.

  • Victor Raymond Jun 20, 2017, 7:01 pm

    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.

Only logged in members may comment: