cutlass bearing

[Seapepper]

During use last summer the prop shaft vibrated badly and on turning the shaft by hand, it seemed to be sticking to the cutlass bearing in the p bracket. After running in gear for 15 min or so, the shaft turned smoothly.
On vieving the bearing out of the water, I found that the shaft was coated with a chalky layer, like limestone, and was also coated inside the cutlass bearing, hence the jerky shaft movement. This layer had worn the cutlass bearing (which was new last year).
The boat is moored in fresh water, but sailed in salt water estuary and the sea. There is a large cement works next to the mooring.
Other local boats do not seem to suffer with this problem!

Given this information, has anyone any ideas :-
1 What is happening?
2 How can it be prevented?
3 Can the fallout from a cement works dissolve in the fresh water and then form on stainless steel?
3 Help!

Seapepper

 

[david_bagshaw]

Q How long was the shaft left stationary?

I have seen shafts pitted from lack of oxygenation in the cutlass area, which would run roughly, & wear the cutlass as described., and probably look shiny or clean after running.

Stainless shafts do pick up a kind of chalk / mud on their surface, but it is usually v soft.

David
www.yachtman.co.uk

 

[Seapepper]

Thanks for the reply.
If the shaft is left stationary from one week to the next, it has the problem. Also, shaft is not pitted, but covered in the chalky substance that you describe.
John