Advice on how to repair this prop shaft please.

[sinnerman]

There is an epoxy repair from a company called "Belzona" which is specifically designed to repair sealing areas on rotating metal shafts.

It is basically intended for industrial use to repair shafts on $$$$$ machinery. The epoxy after cured, is machined to the original shaft diameter/ finish.

a video:

https://www.youtube.com/watch?v=U75s9XNruBQ

marketing pdf:
https://www.belzona.com/assets/data/...al-repairs.pdf

Cheers.

[Nicholson58]

Originally Posted by JeremyFowler

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...

Take it to a machine shop. Turn down the damaged area to totally smooth. Deliver it to a plasma spray metal shop and have the low areas built up with very high nickel-chrome steel. Turn and polish to size. This may cost as much as a new shaft but the wearing surfaces will be immune to further damage.

We did this on our Hundested 1984 vintage 50 mm shaft. $20,000 replacement. I did all of the machining. Total cost $600

[pendragon]

Have you considered cutting an inch or so of the shaft at the coupling end , so that the corroded parts are not in contact with the gland?
iow cut of half the distance between the corroded patches
Or just tig weld (316) Put the shaft between centers on a lathe and heat (oxy/acet)& cool the opposite side until straight to within 0.05mm .
Alternatively press it straight on a hydraulic press

[Ninedotsix]

Originally Posted by JeremyFowler

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!

I think I saw all of the posts, so if there’s one where the following question has already been asked, then my apologies.
Being conservative, I definitely would put safety first, and not lose my prop or go broke shaft in a seaway.
But I wonder if you have an oversized (let’s say generously sized) shaft section for the size engine?
It happens when people think bigger is better, or transplant an engine/tranny to use with existing shaft (typically resulting in undersized shaft if the idea was to increase power).
So, my point is to ask the shaft OD and engine HP and whether with the engine involved, would a smaller shaft suit? If yes, then torque shearing is less concern.
I’ll leave it to others to debate stress corrosion, which can happen from welding, and will make it start breaking up on the welding bench.
It triggers my memories to think about chasing stress cracks with TIG, watch the cracks propagate faster than I can weld them together. Then, back off and look to see the shaft cocked over in a bend.
So, only after verifying that the full OD of the shaft is not needed to transmit the torque, would I run a shaft in that condition.
For instance, if it’s a 1” shaft, and the engine prop and boat need 3/4”, you may reposition the shaft in the gland, or epoxy the gland running surfaces, and go ahead to run awhile longer. If so, watch the hand on the shifter to avoid shock loading going FWD-REV or vis-versa.
But, if you can get a replacement Aquamet shaft for 1/2 a day’s machine shop charges, just go new.
Money well spent on peace of mind, my $0.02
PM

[Mickeyrouse]

Welding will also change the metallurgical properties of the shaft in unpredictable ways. I’d recommend a new Aquamet shaft. Seems like I paid about $180 for a four ft. section of Aquamet 19. Aquamet is also available as Aquamet 21, a subtle increase in strength likely not perceptible in 1” shafting for sail propulsion.

[more]

Originally Posted by Mickeyrouse

Welding will also change the metallurgical properties of the shaft in unpredictable ways. I’d recommend a new Aquamet shaft. Seems like I paid about $180 for a four ft. section of Aquamet 19. Aquamet is also available as Aquamet 21, a subtle increase in strength likely not perceptible in 1” shafting for sail propulsion.

marine shaft is made from
SS AISI 630
aisi 316L
AISI S31803
also lot aneled shaft is possible but not for our use need.

AISI XM-21 ,AISI XM-19 ,AISI F51 / F60 , stainless steel grade 1.4571 , 1.4462 duplex stainless steel and many others around the world.

[more]

But if i see like this guy on my boat i try to made shaft from AISI S31803

[Mike Burch]

Originally Posted by George DuBose

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.

Less than $300? Not in New Zealand, it wouldn't!



But whatever the price, it's going to be better in the long run to get a new shaft made. That amount of corrosion is simply not repairable to a satisfactory standard. Yes, it's almost certainly 316, but I can tell you from personal experience of welding 316 and attempting to turn 316 welds that you'd be on a hiding to nothing.

[more]

Originally Posted by Mike Burch

Less than $300? Not in New Zealand, it wouldn't!



But whatever the price, it's going to be better in the long run to get a new shaft made. That amount of corrosion is simply not repairable to a satisfactory standard. Yes, it's almost certainly 316, but I can tell you from personal experience of welding 316 and attempting to turn 316 welds that you'd be on a hiding to nothing.

in minute surf in Croatia i find ready made prop shaft from 70€ to 700€ price rang

but this ready-made prop shaft is not good in today's delivery guy days.
nobody can warranty this shaft is not curved in transport.

for example redy made shaft very expensive spain company
https://forboat.eu/boat-accessories-...rice&order=ASC

but shaft AISI 630 (MARINOX 17) 40mm meter is 9,87 kg old price is 7€ kg

[Ballsnall]

Originally Posted by Ninedotsix

But I wonder if you have an oversized (let’s say generously sized) shaft section for the size engine?
PM

As Nine.6 suggested, if you are comfortable with the shaft strength in its current condition there are probably several cheap fixes. There's a product called speedy sleeve that will go over the damaged section or a method I would use is to grind out the pitting and fill with brazing rod filler. File and sand to round and you should be good to get a few more years use.