Propellor shaft replacement

[Andrew Watt]

The prop shaft on my 3 1/2 year old 36i has dangerously severe corrosion, between cutlass bearing and propellor. Underwater is inspected regularly and anodes have been replaced when necessary. I don't know the cause of this - maybe a bad batch of shaft material.
I am based in Thailand and need to source a new prop shaft. Does anyone have suggestions for a supplier (globally) .
Maybe I can have one manufactured locally, but it is difficult to find 25mm shafting.
Anyone any suggestions?

Andrew (Sansanook 36i)

[MalcolmP]

Andrew

Almost certainly electrolysis. Always a black art, anodes have to be fully bonded and the surface clean (once they scale up they become ineffective) so electrolysis can still occur even if you have anodes fitted etc

You should be able to get an OEM shaft ordered through
Martin Holmes at Lee Marine in Phuket
Tél. : [phone]
www.leemarine.com

[sailbleu]

You can start here , and have it send to Thailand.
www.jeanneauparts.com/en/index.php?cp_sid=1319470a4f32a&cp_tpl=main
Not sure if you can access the site any further because I can't for some time now. Dont really know the raison for that being so.
Does anyone have the same problems ?

Anyway , what you experience - the corrosion that is - isn't normal , by far.
Are you staying in a port ?
If so , are there any neighbours with the same corrosion prob ?
Your boat , or someone elses could have an electrical leakage of some sort destroying metal in the vicinity.
I've seen that happening (a victims story) in the port where I winterstay on the hard.
Propellors halfway gone , pinholes in metal boats leaking diesel , all because one boatowner had made a wrong AC connection.

Good luck

[sitara]

Andrew,
Good luck sourcing a new prop shaft.

Just as a matter of interest what is your propeller made of? If it is bronze I would have thought that would vanish before the shaft.

Rob

[ianqv]

Hi Andrew,

It does sound like electrolysis!!
You may have some stray voltage knocking around, a good start would be to check as suggested above. If ok start to look deeper.... engine earths and so on. If you have a good multimeter, and with engine off - check to see if you have any stray voltage on you prop shaft.

Do you have any pictures of the old shaft?

Regards

Ian

[flightdeck]

Forum: "prop shaft pitting" by offshore, there may be some info to be found there.
Cheers

[Andrew Watt]

Thanks for the advice. My boat will stay in the water until the spares are available. It looks like a local manufacture will be the best (far cheapest) option for a new prop shaft. I will post photos of the old shaft when it is removed and check the electrolysis issues. Strange that the problem has only become serious in the last month or so. The boat has been in the water for 3 1/2 years with minimal corrosion.

[electricmonk]

I ve had 2 jeanneaus, a 37 and a 43 BOTH suffered advanced crevice corrosion of the propshaft, both were renewed with "duplex stainless" made locally (UK) with no further issues, the scrap men (two different ones a couple of years apart) would not accept the old shafts as stainless steel.

Edit: The anodes were all in good order on both boats and a galvanitic isolator was fitted. No problems with dezincification of the propellers. Crevice corrosion is a very "local" form of corrosion, which in my understanding is attributed to poor quality materials.

[ianqv]

This is what I've been thinking your prob could be!! are you plugged into the mains all the time?
If so, the prob may NOT be with your boat - but an earthing concern on your pontoon!!!

See www.galvanicisolator.co.uk/

Regards Ian

[fstbttms]

Sun Fast 35 shaft. Looks like a repair to the shaft had been done at the factory and subsequently failed. Soory for the large size and poor focus.

[davideso37]

Another propeller shaft replacement.
The 6 year old prop shaft on our SO37 was found to be pitted on the annual haul out for antifouling. We are on a swing mooring with no chance of stray currents so it appears to be a metal quality issue.
Also the four year old maritec bearing we used instead of the rubber Jeanneau supply has excessive wear so that was not the solution it promised to be. The yard feel the bearing is too small for the engine and prop size but I will stick with it for now if we get four years a bearing instead of the two with the rubber.
Regards
David

[Toby]

Apr 16, 2012 8:11:01 GMT davideso37 said:

Another propeller shaft replacement.
The 6 year old prop shaft on our SO37 was found to be pitted on the annual haul out for antifouling. We are on a swing mooring with no chance of stray currents so it appears to be a metal quality issue.

Hi, exactly the same thing happened on my boat. 2004 SO37, berthed at a marina. My zincs were working as normal, replaced every 4 months or so, whenever they had lost substance enough. In my case I suspect a stray current, but not sure it came from the boat or from the marina.
The prop shaft was replaced after we found the holes. Funny enough, the holes were nicely spaced, about 20cm in between them. Had to have a custom job from a machine shop in 316 stainless steel. Replaced the cutlass bearing and the shaft seal as well.