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Old 02-02-2022, 18:10   #1
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Advice on how to repair this prop shaft please.

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...
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Old 02-02-2022, 18:13   #2
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Re: Advice on how to repair this prop shaft please.

I see a new shaft in your future….judging from the photo alone that amount of material loss is fatal.
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Old 02-02-2022, 18:17   #3
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Re: Advice on how to repair this prop shaft please.

It definitely can be welded & machined but the trick is in the straightening as ss bends like a b*****d with welding.
I'd give it a try but If you have access to a lathe , mill. press & can machine the taper & the thread/keyways new shaft stock is not that expensive if your shaft aint too big/long.
It depends how much of a factor time is really.
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Old 02-02-2022, 18:49   #4
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Re: Advice on how to repair this prop shaft please.

If you were my customer asking that question, I'd tell you to replace it. Trying to repair it is throwing good money after bad, IMHO.
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Old 02-02-2022, 20:13   #5
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Re: Advice on how to repair this prop shaft please.

This bloke makes it look easy but believe me if you aren't doing it all the time it isnt.
Anyway you can get the idea of flame straightening.
I wouldnt be concerned about strength or corrosion if you polish & passivate after welding
, the straightening will be the battle
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Old 02-02-2022, 20:25   #6
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Re: Advice on how to repair this prop shaft please.

Some of those corrosion pits look pretty deep in your photo. This shaft, in my opinion, should be replaced. If that were my boat I'd replace that shaft.

If you were my client, and insisted on welding it, I would mandate a complete chemistry analysis be performed so that I knew the exact alloy including the carbon content of that shaft. That analysis will cost you close to $1000 and it can't be done on-site. You would be required to take destructive samples to send to a lab for this analysis. Depending upon your current shaft you might not even be able to do this and still be able to use this shaft. This would be a "must have" analysis as it will drive how the shaft would need to be welded; from the selection of filler metal to potential post weld thermal processing. The amount of work to do a reliable weld repair would have many out of pocket expenses before you even get to welding. I would not recommend this route nor would I do it for any boat I might be involved with.

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Old 02-02-2022, 20:57   #7
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Re: Advice on how to repair this prop shaft please.

Metal analysis???, lol. 99.99% chance its 316L on a Kiwi production boat of that era.
Mountain out of a molehill springs to mind.
Of course, in theory, analysis is essential but this is a DIY job
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Old 02-02-2022, 21:45   #8
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Re: Advice on how to repair this prop shaft please.

I'm a Toolmaker and I can tell you that it should not be done. A TIG build up and then turned will probably stress bend the shaft. Also the filler rod will likely be a miss match and cause further corrosion. It could be 316 or even Aqualoy. Buy a new shaft.
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Old 02-02-2022, 21:48   #9
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Re: Advice on how to repair this prop shaft please.

That shaft is toast,the corrosion on the outside is the small part ,probable,all most certainly much more on the inside ,new shaft 2205 or 316l the machining costs will be the same ,weld it and it breaks in use ,your back to the start .⛵️⚓️
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Old 02-02-2022, 22:33   #10
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Re: Advice on how to repair this prop shaft please.

Agree, that looks terminal and far from just some minor pitting or marking.
If you were in the middle of no where, maybe some welding would buy you some confidence to get home.

If your pulling it out of the water and removing the shaft you might as-well just replace it. Always going to be a weak-point and on the back of your mind.
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Old 04-02-2022, 05:40   #11
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Re: Advice on how to repair this prop shaft please.

Does the shaft need replacing if you could move the gland to contact the shaft at a different location?
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Old 04-02-2022, 05:56   #12
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Re: Advice on how to repair this prop shaft please.

A new high quality prop shaft would be less than $300. You can send your shaft to get a perfect duplicate. Prop shafts do wear and need replacement on occasion.
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Old 04-02-2022, 06:25   #13
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Re: Advice on how to repair this prop shaft please.

The only structural way to repair would be welding and machine, however, the weld distortion will bend the shaft and it is very hard to get straight. You will likely have vibration... as others said, I think you need to replace with a new one. There are Epoxy repair options to get the smooth surface back if this is in a seal area. But an Epoxy repair will not provide structure and I wouldn't be happy as it's a matter of time before this cracks... just a temporary band aid
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Old 04-02-2022, 06:59   #14
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Re: Advice on how to repair this prop shaft please.

I ran 1 1/4” shafts with some amount of crevice corrosion for many years. The stuffing leaks became an issue, so i put on dripless seals. 350hp hi rpm gas motors x2

I suspect your power to shaft size is far more acceptable, plus likely shorter/cheaper. I would not repair, but replace.
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Old 04-02-2022, 10:03   #15
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Re: Advice on how to repair this prop shaft please.

Quote:
Originally Posted by fstbttms View Post
If you were my customer asking that question, I'd tell you to replace it. Trying to repair it is throwing good money after bad, IMHO.
Correct answer IMHO. I've owned a machine/fab shop for 40 some odd years. This could be turned down to good metal and built back with weld, straightened and turned again... if that was your only option. This is time consuming and thus expensive.
So do what I did, call these guys:

https://www.generalpropeller.com/ind...te=common/home
Very reasonable price and lead times.
I couldn't buy the material and program the machine and proof it out for what they charged me. The quality is first class. (no affiliation)
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