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Old 04-02-2022, 10:09   #16
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Re: Advice on how to repair this prop shaft please.

If the corrosion is limited to the gland location it is typical crevice corrosion due to oxygen starvation.
Clad welding can be done satisfactorily but, in my opinion once you add the cost of preparing the base metal, welding, machining and heat straightening, the job will be expensive and might only provide a temporary fix. Renew the shaft if you can.
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Old 04-02-2022, 10:26   #17
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Re: Advice on how to repair this prop shaft please.

Crevice corrosion on the prop shaft usually occurs where it goes through a packing gland etc. depriving it of oxygen. (Same problem with SS chainplates that have one side stuck to the hull - they may look shiny on the outside...) The problem with crevice corrosion in SS is that while it may look like a surface blemish, it will run deep like a cavity; any machine shop familiar with prop shafts would tell you to replace it.
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Old 04-02-2022, 11:41   #18
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Re: Advice on how to repair this prop shaft please.

I'd consult a machinist and a welder. Not someone I know that can weld. In short a new shaft may be cheaper.
A good machinist is hard to find.
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Old 04-02-2022, 12:05   #19
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Re: Advice on how to repair this prop shaft please.

That's not a shaft it's scrap metal.
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Old 04-02-2022, 12:15   #20
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Re: Advice on how to repair this prop shaft please.

So how do the experts prevent the pitting from recurring on the new shaft? Use the boat more often?
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Old 04-02-2022, 13:26   #21
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Re: Advice on how to repair this prop shaft please.

Do your internet research and find a shop that will make you a new prop shaft.

If not NZ, then Australia, Philippines, .

Worst case USA/UK.

Welding will change the material structure..

This is stainless and a crack can propagate from the pitting resulting in shaft failure.

I am in Houston Texas and we a have a machine shop (P&V) that are the local gurus for making new shafts. Since sailboat shafts do not have any splines, they are easier to manufacture.

Hardest part is the taper at the propeller end. The rest is a straight piece of stainless rod with some threads and a keyway....

The shops can also mate up the coupling and touch it up on the lathe to make it sure is "true" to the shaft and has no axial runout / wobble (it seats perpendicular at 90 degrees to the shaft axis...)

My two cents.

Cheers
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Old 04-02-2022, 13:29   #22
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by JeremyFowler View Post
Expert SS repair advice needed please!
This is what I found when I removed the shaft. Seems to be corrosion pitting? And seems to be right where the gland is too. Can it be repaired by welding and then turning down on a lathe? If so, what precautions should be taken? It seems it's a complex subject, judging from the bit I've researched on
Google.
I know someone who can weld well, using TIG, MIG, or stick. And I have access to a lathe and dial gauge also. But I wouldn't like to do a seemingly easy repair if it is going to bite me further down the track when the engine is back in and the boat is back in the water... Although saving some dollars is definitely worthwhile, at this stage of the game...
Very common. I have mentioned it many times. As mentioned, the water sits in the gland, SS is more subject to corrosion when de-oxygenated water sits. New shaft needed. If a boat sit's on the hard it still occurs from the trapped moisture.

If you run your engine in gear regularly it will help.
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Old 04-02-2022, 13:36   #23
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by donradcliffe View Post
So how do the experts prevent the pitting from recurring on the new shaft? Use the boat more often?
If one makes the shaft from 2205 s/s or one of the special shafting cupro-nickel
alloys the likelihood of such pitting far less.

My 2205 shaft is now 32 years old and does not show any pitting.

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Old 04-02-2022, 13:47   #24
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by donradcliffe View Post
So how do the experts prevent the pitting from recurring on the new shaft? Use the boat more often?
Jim ^ is right. Monel (cupro nickel) used to be more common and far better than common SS for shafting.
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Old 04-02-2022, 14:17   #25
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Re: Advice on how to repair this prop shaft please.

If you were in a remote part of the world and you needed to get that shaft in to get you some pace in short duration. I'd do the following.
Clean out the pits, polish them, make any sharp edges smooth. Thing is you got to avoid the crevice corrosion, that happens in a corrosive environment with fluctuating stress, you got both these.
Downside is that if it fails, you lost a propeller as well as a large hole that could allow water in. Sail in company, have contingency to hand.
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Old 04-02-2022, 14:26   #26
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by JeremyFowler View Post
Expert SS repair advice needed please!
This is what I found when I removed the shaft. Seems to be corrosion pitting? And seems to be right where the gland is too. Can it be repaired by welding and then turning down on a lathe? If so, what precautions should be taken? It seems it's a complex subject, judging from the bit I've researched on
Google.
I know someone who can weld well, using TIG, MIG, or stick. And I have access to a lathe and dial gauge also. But I wouldn't like to do a seemingly easy repair if it is going to bite me further down the track when the engine is back in and the boat is back in the water... Although saving some dollars is definitely worthwhile, at this stage of the game...
Stainless Products ltd 5-6 kg 1 meter and use your lathe guy
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Old 04-02-2022, 14:52   #27
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Re: Advice on how to repair this prop shaft please.

If you're going to buy new shafting, buy monel and never have to do it again.
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Old 04-02-2022, 15:48   #28
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Re: Advice on how to repair this prop shaft please.

Thanks for the advice everyone, although not what i was hoping for... How often it is that the worst is actually the best.
Will go the new shaft route...
Cheers!
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Old 04-02-2022, 16:03   #29
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by JeremyFowler View Post
Thanks for the advice everyone, although not what i was hoping for... How often it is that the worst is actually the best.
Will go the new shaft route...
Cheers!
possible also repair ,but you must find somebody who work spray building shaft. usually use on heavy machine where is shaft 5000$ and more.



you can also tig weld shaft but you need machine. in my town we have one 12 meter long machine and big in marine diesel engine factory. but hour work is over 5000 € and more is cheaper buy new shaft .
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Old 04-02-2022, 16:08   #30
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Re: Advice on how to repair this prop shaft please.

if you really don't have money. buy tig electrode 3,2 mm 316L
and use this tehnic
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