Lucky find under prop

[Rick D]

I was lucky the yard decided to pull the prop. Bad electrolysis. Aquamet shaft, twenty years old. Prop is stainless folder. Was on a hot dock for seven of those years, but not in the last seven. Looks like s/s corrosion rather than electrical leakage to me; prop is fine. Current prop on for ten years. This could have been expensive if I'd lost the prop!

 

[Ralph Johnstone]

Corrosion can proceed in some pretty unusual ways.

What condition was the interior surface of the bore on the SS folding prop .............. discoloration, pitting, anything ? ? ? ?

I would think that the prop was more than just slightly cathodic to the shaft. Or the shaft was something less than advertised Aquamet.

Aquamet is pretty good dealing with low oxygen but yours really seems to have taken a hit. Any chance of checking for a galvanic voltage with the old removed shaft and the prop thrown in a bucket of warm salt water ?

 

[Charles Erwin]

Aquamet shafting is designated 17 19 and 22 which refer to the alloys from which the shafting is made. There is also Aqualoy and other similar names for shaft made by different companies. The corrosion resistance depends on the alloy - the less corrosion resistant the stronger the material typically.

As Ralph has noted - your photo looks typical of crevice corrosion which is always a problem where water is not circulating - like shafts in long stern tubes or in your case joints where water gets in but cannot get out. Such waters become oxygen starved - and stainless alloys need oxygen to resist corrosion.

By the way it looks like the propeller was not all that well lapped to the shaft to start with so when you replace the parts see to it the shop you use knows what they are doing.

Charles

 

[rgranger]

This could have been expensive if I'd lost the prop!

Uhmm.... looks expensive as is...

 

[Rick D]

It is....

Uhmm.... looks expensive as is...

....expensive; about a thousand with the new split coupling. It's available for much less through this site. However, I was in a bind and need it now. So, I went to a shaft specialty machine shop in Los Angeles. This is a small job for them.

 

[Jellis]

Thanks for the advice. I had a haul out scheduled before this happened and was waiting until the marina service department had hauled out those who made their reservations before I did. Then unprecedented rains came and all the marina service departments on the lake are literally under 10-15 feet of water and may be inoperative for months. Unless the job can be done by divers as the boat sits in its floating slip, I'll miss most of the summer boating season. I'll confer with some divers and see what they say they can do.

 

[WayneH]

Thanks for the advice. I had a haul out scheduled before this happened and was waiting until the marina service department had hauled out those who made their reservations before I did. Then unprecedented rains came and all the marina service departments on the lake are literally under 10-15 feet of water and may be inoperative for months. Unless the job can be done by divers as the boat sits in its floating slip, I'll miss most of the summer boating season. I'll confer with some divers and see what they say they can do.

I was thinking that now would be a good time to move your boat to the yard. Then get a diver to put the jack stands under it and wait for the COE to drop the lake level.

 

[justsomeguy]

I was thinking that now would be a good time to move your boat to the yard. Then get a diver to put the jack stands under it and wait for the COE to drop the lake level.

Brilliant!

 

[rgranger]

I was thinking that now would be a good time to move your boat to the yard. Then get a diver to put the jack stands under it and wait for the COE to drop the lake level.

To soon....