heavy vibration when in gear

[slingsby]

Back in the water this week and have replaced the cutlass bearing and volvo shaft seal. I've realigned the engine (VP2003)now its in the water and got it to within .003 at the flanges, fitted an R&D flexible coupling and everything runs fine until you put it in gear.....Then at low revs the engine is bouncing all over the place and has to be shut down quickly.
At the end of last season I noticed some vibration at high revs, hence the replacements this year.
Has anyone got any ideas what might be wrong? I'm thinking engine mounts, but surely they could not fail so drastically whilst ashore? Any help would be greatly appreciated

 

[Thistle]

What kind of prop? Problem with one blade of a self-folding one? Or could you have picked up something on one blade?

Why did you have to put in the flexible coupling if it's within 0.003 at the flanges? What's the alignment like without the coupling? Did you shorten the shaft to get the coupling in?

 

[slingsby]

Its a fixed 2 blade prop. I fitted the Coupling as a 'belt and braces' move and didn't need to shorten the shaft.

 

[Plevier]

With the Volvo shaft seal which provides little axial location, isn't it normal to have a rigid coupling? With a flexible coupling, the shaft is only firmly centred at one point, the rear cutlass bearing. Aren't flexible couplings for when you have a bearing at the front of the shaft tube?
That was my impression - could be wrong.

 

[earlybird]

The R&D coupling is quite stiff, my prop-shaft is a basically similar arrangement except that the seal is a PSS. Works fine with my 3-cyl. Beta.
For starters, I'd have a second look at the mounts to see if your adjustments have left one of them with little or no load on it, despite the apparently good alignment.

 

[Skysail]

With the Volvo shaft seal which provides little axial location, isn't it normal to have a rigid coupling? With a flexible coupling, the shaft is only firmly centred at one point, the rear cutlass bearing. Aren't flexible couplings for when you have a bearing at the front of the shaft tube?
That was my impression - could be wrong.

+1. I think I have seen that recently. And as the coupling is the only factor to have changed, it's where I would look first.

 

[Caer Urfa]

Has anyone got any ideas what might be wrong? I'm thinking engine mounts, but surely they could not fail so drastically whilst ashore? Any help would be greatly appreciated

Not 100% sure what your coupling looks like,maybe a long shot but from personal experiance you can assemble a flexable coupling wrong, ie the mounting surfaces only go one way and have you got the tie plates mounted correctly?


Mike

 

[Neil_Y]

Bearing carrier alignment?
At low rpm the bearing is effectively dry (no water film established) with a bearing out of alignment the shaft can run around a bearing. Could you rotate the shaft easily by hand with the new bearing?

 

[scottie]

If you know that nothing will be affected then try taking the R&D out

 

[PCUK]

Check there is nothing on the prop' before you do anything else. Unless a blade has fallen off nothing else can cause such bad vibration. Certainly nothing to do with the coupling.