Re: [Amel Yacht Owners] Modified SM Prop Shaft Seal Bush

Ian Shepherd


I believe that you are over complicating the issue. As far as  I remember the seals were from a local seal shop in Larnaca. I have no idea of the hardness but I can check when I get there next week as I bought more than I have used.

As far as the stainless is concerned, just plain old 316 is all I know. As Heinrich is no longer with us, I cannot find out, but maybe someone can test the bush which I still have.

The thing is Bill is that you are advocating people remain with a situation that we all know lets us down unexpectedly and often at an awkward time. You say you worry about protecting an expensive system yet you encourage owners to suffer sea water mixing with the lubricating oil. When this happens not everyone is in a position to haul out immediately. More damage may  be done if this happens

The benefits of what I have proven are:

The bush does not wear at anything like the rate of a bronze one.

As a result, it is now highly unlikely that the oil will be contaminated between say three year haul outs.

There is no electrolysis problem with stainless on stainless. at least not if lubricated with an anti corrosion grease such as Corrosion Block.

The fact that Amel are experimenting with a stainless surface indicates that this is the way to go. I am so glad that Amel have latched onto the idea, as they have with my idea of using sealed bearings in the bow thruster. Maybe they will look at a stainless sleeve on the bow thruster shaft too. It works!

You can protect the past all you want Bill, but my goal is to reduce nuisance servicing to the minimum so that I can enjoy sailing the boat.

Sometimes it pays to think outside the box.

Not sure about the mileage accolade. 48,273 as I speak almost all single handed. But then on an Amel that's easy!

Kindest regards to you and Judy

Ian Shepherd SM2K 41 Crusader (2003) Kasteloriso Island Greece

On 07/08/2017 14:48, 'Bill & Judy Rouse' yahoogroups@... [amelyachtowners] wrote:
Ian, All, and especially newbies;

Most of you know that I have been and will always be the person in this group that warns everyone about changing an Amel design. It is nothing personal. I love all things Amel and I take it as my responsibility; so, because of that responsibility, I will offer the other side of CRUSADER's report and recommendation...nothing personal, but I am the self-appointed protector of all things Amel, and will always be the one to point out the RISK vs the REWARD in changing an Amel design.

I am certainly no expert, but I believe that stainless steel comes in at least 5 types and also different hardnesses; and the Nitrile Buna-N seals are made in different hardnesses. Although I personally do not need the answer to the following questions, I believe anyone attempting to follow your recommendation should know: What type of stainless steel and hardness you used? What was the hardness of the seals? What were the engine hours between servicing?

I would guess that to obtain different results than the Amel-proven system, you have to either scientifically solve the wear issue to achieve a different balance between wear of the seal and wear of the bushing, or use a trial and error method. I assume that your method was trial and error, which resulted in changing the balance of wear between the wear bushing and the wear on the lips of the seals; which extended your haulout interval - your goal. 

We must remember that there will be wear between the lips of the seal and the wear bushing on the C-Drive. It is obvious to anyone who has serviced an Amel C-Drive that with the current Amel design the wear bushing appears to wear more than the seal lips. 

I would assume that one could scientifically change the balance to increase the interval of haulouts. However, it makes sense to me that unless a scientific approach is used, we would be playing Russian roulette with a very expensive part of our boat.

Don't take what I am saying as criticism. I am happy that you achieved your goal. My goal was to haul out every 2 years for more reasons than C-Drive maintenance.

I would urge all readers of this message to stick with proven Amel supplied parts and procedures, rather than changing something that you do not completely understand. I do not have the metallurgical and mechanical engineering expertise to develop a better system than Amel's wear bushing and seals, nor do I believe any of us have that knowledge. 

And, I will take this a step further: Many of the Amel systems that I have been exposed to, obviously take into consideration the required maintenance and the level of experience and knowledge of the person performing the job. When I managed new product development, I used the term "child proof." When I asked my staff if the new product was "child proof," they knew that I was asking if it would pass the test of the most ignorant user. I never met Henri Amel, but from my experience with his boats, I believe he also used my term, or one similar.

Until recently, I had no idea that the Nitrile Buna-N seals are available in a hardness range from 40-90, and I do not know the hardness of the Nitrile Buna-N lip seals that Amel uses. We all know that bronze, brass, and Naval brass are available in different hardnesses. I suspect that none of us know the hardness of the wear bushing that Amel uses, nor do we know the percent of copper, tin, and zinc . Without this information, I believe that changing the balance of wear between the bushing and the seal should not be attempted, unless you understand the huge risk for what, I believe, is very little reward.

Ian, it is very good to have you return to this forum. I have missed you and your posts. Probably none of us have more miles in a Super Maramu than you have.


CW Bill Rouse
Admiral, Texas Navy
Commander Emeritus
Amel School
720 Winnie St
Galveston Island, TX 77550

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