Propeller shaft, coupler and struts - Page 2 - SailNet Community
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post #11 of 26 Old 07-15-2014
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Re: Propeller shaft, coupler and struts

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Originally Posted by Westsailforever View Post
Strut should be bronze not SS .
And not 1.5 to 2k either!

Brian
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post #12 of 26 Old 07-15-2014
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Re: Propeller shaft, coupler and struts

Bronze contains about 15% zinc. When the piece suffers from electrolytic corrosion (either galvanic or stray current) the zinc dissolves leaving the bronze with a pinkish hue and visible pitting on surface. A strut in this condition is seriously weakened. I have seen a strut break under power and stay on the shaft getting whipped around 800 (shaft) RPM and digging a hole in the hull before the shaft fell out.

Not enough information provided to say if the cause is galvanic or stray current but it is certainly not "electrolysis" which is a commonly misused term by those who do not understand electrolytic corrosion. Galvanic corrosion is a fairly slow process while stray current corrosion can be a shockingly (pun) fast process. If stray current is the culprit you may have an electrically unsafe boat.

Can't tell from the photo but your propeller must also be suspect. Very few propellers are bronze, most are actually manganese bronze which is actually a brass which contains around 35% zinc. If the strut is compromised the propeller is in likely worse condition.
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Last edited by boatpoker; 07-15-2014 at 06:33 AM.
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post #13 of 26 Old 07-15-2014
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Re: Propeller shaft, coupler and struts

The coupling is finished. The stuffing box and shaft maybe salvageable. Then change the cutlass bearing, and stuffing. Now if your lucky, and the strut survives the removals, add some fiberglass to support the root of the strut.
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post #14 of 26 Old 07-15-2014
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Re: Propeller shaft, coupler and struts

I just did this job on my boat back in may. We were pressing the cutlass bearing out and the strut fell apart. This work must be done on the hard so if your out now, fix it now. It's not rocket science. Get a 4 1/2" grinder and split the coupler. You can't change the stuffing box gland w/o removing the coupler.
If the strut fails, (trust me it will happen when you really need the motor) the flailing prop and strut can hole the boat. Forget about the fiberglass BS. Fix it properly before you leave.
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post #15 of 26 Old 07-15-2014
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Re: Propeller shaft, coupler and struts

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Originally Posted by thevdeub View Post
How bad is it ?
We hauled the boat (Tartan 37', 1977), planning to install a drip less packing gland.
Now, the yard seems to think the strut is really weak and should be changed, and it is unlikely that the shaft will ever come out of the coupler and is corroded inside. I would expect the bill to come down with a full new shaft and strut, i.e. 3 to 5k$.
Other people tell me that this is expected on an old boat and there is nothing to really worry about.
I would prefer plan the full repairs in a couple of years, if this is not 'unsafe'.
In a couple of years, I might have more time to plan for this financially and maybe do the work myself.

Any opinions ? Can I wait ?

ps: I am planning for a pacific crossing, CA to HI, not much motor involved, if any.

That strut is beyond gone and dezincification has won the battle.....

Contact Brewer's South Freeport Marine in South Freeport Maine. They just did a Tartan 37 strut and had it custom cast because they are simply not available. John Brewer should be able to tell you whom he had cast the strut. I believe it was in Mass.

With the strut looking like that I would move forward with a full corrosion survey by a competent corrosion specialist. Your board, board pin. thru-hulls etc. could also be damaged.
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Last edited by Maine Sail; 07-15-2014 at 04:58 PM.
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post #16 of 26 Old 07-16-2014 Thread Starter
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Re: Propeller shaft, coupler and struts

Alright. Another picture grinding the .5mm of pink layer. If I understand correctly, the metal is deeply weakened, and not only in surface. The gold/Yellow layer looks really stronger than the pink cupper in surface. This is not rocket science but a lot of work and a very inaccessible area (Hot Water tank, ...), and I woould have preferred attacking this in one year or so, with more time in front of me and in a cheaper yard.
I have been quoted for 400$ for the pattern + 600$ for the strut. Add a coupler, a shaft ...
Anyway, thanks for the feedback. and the contact in South Freeport, Maine.
Cheers
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post #17 of 26 Old 10-03-2014 Thread Starter
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Re: Propeller shaft, coupler and struts

For the archives.

We ended doing the work professionally. We had to change the shaft as well, and the packing gland. Overall, adding Strut and Coupler, it ended up almost 2K for the parts.
The bronze strut has been made by marine hardware .com based on the template of the old one. I did all the cleaning, removal etc.. myself, but putting back everything together and aligned - professionally - came back around 1.5K.
Close from the original estimate. But at least, the job is strong and well done, and I should be good for the next 20 years.


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post #18 of 26 Old 10-03-2014
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Re: Propeller shaft, coupler and struts

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Thanks for comming back with the follow up. A lot of folks don't and it is really nice to see how things work out.

Looks awesome.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #19 of 26 Old 10-03-2014 Thread Starter
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Re: Propeller shaft, coupler and struts

Thanks. It took a while to close this thread, because it took actually a while to get it done. Overall, almost took 2 months (!!!!). 3 Weeks to get the strut done, we had some parts issues, the yard was busy, etc... Make sure you have a good yard that do not make pay the lay days while waiting for parts
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post #20 of 26 Old 10-04-2014
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Re: Propeller shaft, coupler and struts

Very smart to get it done. From personal experience it's a real PIA when things like this need to be done but well worth it once finished.
Have a safe voyage
Jim

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