Shaft Bearing, outer diameter?

[dahlke]

When I rev up my fateful old MD6A (only when in gear) I can feel some shaking and there is a sound. I've checked the engine mounts they all seem fine. I'm thinking it must be the shaft bearing. Are there any other common reasons for this behavior? Assuming it is a worn shaft bearing I should properly replace it before the big summer cruise right? A bit of a pain having to hall out Obelix after only 3 weeks in the water Luckily I still have 4 weeks left to fix the problem

What is the outer diameter of the shaft bearing? 38,1 mm? (I believe the shaft diameter is 25 mm).

[Sanlen]

Your probably right about the shaft bearing, it can come loose and cause vibrations. I can check the outer diameter on Sanlen tomorrow.

The vibrations may be caused by other things as well. Is the engine in line with the prop shaft? Is the folding prop ok? The metal arm that holds the shaft bearing can also come loose itself and cause shaking (probably not the cause here).

Can you record the sound and shaking and share it?

[dahlke]

I would be very grateful if you could check the outer diameter

I did notice a similar sound last summer (when i sailed the boat home). When I got the boat on the hard i had a look at the arm that supports the shaft and noticed it moved a little when I applied force. A closer look revealed some delimitation in a previous repair. I grinder down to solid fiberglass and applied several layers of woven glass + epoxy. After it had cured there was no movement in the arm what so ever. I had hoped that would fix the problem. I'm pretty sure it's the same sound I heard last summer.

I'll try and record the sound the day after tomorrow

[dahlke]

P.S I'm starting to feel I owe you a nice cold beverage of your choosing if our paths ever cross Thanks so much for all the help Jan

[Bob McGovern]

Could be lots of things. Cutless bearing is the simplest (and can be fixed in the water, but that's an exciting procedure!). Could be mounts; sometimes they look okay but are soft, or delaminated inside. Could be shaft alignment, coupling, or a bent shaft. Prop shape or balance. Or an internal problem with the transmission. Cutless bearing is the usual culprit -- IIRC, side to side play of the shaft in the bearing should be less than 2mm. Of course, other issues like a bent shaft, unbalanced prop, or mis-aligned coupling will cause the Cutless bearing to wear prematurely.

Have you already taken apart the coupling, just to see how well it aligns? May be able to rebalance that w/out having to pull the boat; and at least the bolts will then be broken free if you DO haul it back out to replace the Cutless.

[TamTam]

Hey,

you are right with 38,1 mm, the shaft is 25mm. We had the same strange sounds from our bearing and replaced it: http://www.tamtam-sailing.de/2012/04/.
After replacement everything is quiet and works fine...
The bearing is a standard sized "Vetus" bearing.
For example from our local store: http://www.svb.de/de/gummi-wellenlager.html

[Sanlen]

Hey,

you are right with 38,1 mm, the shaft is 25mm.

Yep, measured the same this morning on Sanlen.

[Sanlen]

P.S I'm starting to feel I owe you a nice cold beverage of your choosing if our paths ever cross Thanks so much for all the help Jan

Just happy if I can help I think this applies for all on this forum

Anyway, a nice cold black Carlsberg would be nice if we should meet up somewhere!