Propshaft pitting

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Propshaft pitting

by Allezcat » Fri Jun 19, 2015 6:31 pm

Has anyone experienced shaft pitting under the Tides lip seals causing leaks? I now have this on both shafts and am considering replacing both Tides seals and moving them slightly so they ride on a smooth part of the shaft. The seals have performed admirably until now.

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Re: Propshaft pitting

by Catrina » Sat Jun 20, 2015 7:23 am

Yes I did.

Had to replace the shafts and new seals. Gregg at Stuart Yachts indicated that it was caused by lack of oxygen in the water around the shafts if the boat sits in the water over long periods of time "without the shafts turning and water flow" which mine did. Turns out that stainless steel requires oxygen to work. Just Google - Crevice Corrosion on Stainless Steel Propeller Shafts.

Now I make sure they get turned every few weeks.

Good Luck,

Catrina - MV34 Hull # 55 - 110HP - 4 Blade props

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Re: Propshaft pitting

by thinwater » Sun Jun 21, 2015 9:27 pm

What sort of anodes are you using?

The absence of oxygen does not immediately mean that stainless will be subject to pitting. It is also generally required that there is a galvanic mechanism in place. Often, this is simply passive SS nearby. However, effective anodes can reduce the problem.

I this case I would suggest taking a look at aluminum anodes. They offer slightly higher potential and are lot prone to deactivation by oxide coating. They are also cheaper and last longer.
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