vibration on prop and dry noise.

[Morphyous]

I had my lister sr2 engine removed, it turned out to be a problem with the reduction unit, it had a hole in the casing. It's bolted directly on to steel bearers, no rubber mounts just spacers, which I left in situ when the engine was removed.

I fitted a new half-tyre rubber coupling, the old one was shot and a Marine engineer fitted the replacement reduction unit and refitted the engine. I've now got vibration (slight wobble) on the prop and the plummer block is noisy. The noise goes when I loosen the plummer block. It appears to be higher above it's mounting spot than the thickness of it's steel spacers, so the plummer seems to me to be pulling the prop downwards when it's bolted down.

 

I'm wondering whether there is possible engine misalignment and whether raising the plummer to eliminate the noise would help any?

[Tony Brooks]

I had my lister sr2 engine removed, it turned out to be a problem with the reduction unit, it had a hole in the casing. It's bolted directly on to steel bearers, no rubber mounts just spacers, which I left in situ when the engine was removed.

I fitted a new half-tyre rubber coupling, the old one was shot and a Marine engineer fitted the replacement reduction unit and refitted the engine. I've now got vibration (slight wobble) on the prop and the plummer block is noisy. The noise goes when I loosen the plummer block. It appears to be higher above it's mounting spot than the thickness of it's steel spacers, so the plummer seems to me to be pulling the prop downwards when it's bolted down.

 

I'm wondering whether there is possible engine misalignment and whether raising the plummer to eliminate the noise would help any?

 

 

It certainly sounds as if something is misaligned.

 

The plumber block should be fitted with the shaft disconnected from the gearbox and in such a manner that the shaft is aligned with the outer bearing and the stern gland. Once that is done the engine needs aligning with the shaft.

 

Now I am not sure what you mean by a half-tyre rubber coupling bu remember the vast majority of rubber couplings only deal with angular misalignment NOT radial. That means, although not ideal, that the axis of the prop shaft and reduction gear output shaft can be a degree or so out of alignment as long as they meet right in the centre of the coupling. They will not cope if the two axies are offset in the vertical or horizontal plane.

 

Its a bit of a bore aligning an engine but as yours seems to be solidly mounted you probably will only have to do it once.

 

FWIW typical gearbox alignment has to be withing 0.05mm . That is 5 one hundredths of a mm.

[Morphyous]

It certainly sounds as if something is misaligned.

 

The plumber block should be fitted with the shaft disconnected from the gearbox and in such a manner that the shaft is aligned with the outer bearing and the stern gland. Once that is done the engine needs aligning with the shaft.

 

Now I am not sure what you mean by a half-tyre rubber coupling bu remember the vast majority of rubber couplings only deal with angular misalignment NOT radial. That means, although not ideal, that the axis of the prop shaft and reduction gear output shaft can be a degree or so out of alignment as long as they meet right in the centre of the coupling. They will not cope if the two axies are offset in the vertical or horizontal plane.

 

Its a bit of a bore aligning an engine but as yours seems to be solidly mounted you probably will only have to do it once.

 

FWIW typical gearbox alignment has to be withing 0.05mm . That is 5 one hundredths of a mm.

The tyre coupling is like a heavy duty rubber wheelbarrow wheel which is bolted between and seperates two sides of the prop, it cushions the prop when the gearbox is put in forward or reverse.

I will try bolting down the plummers block (everything seemed aligned before the engine was removed). Then disconnect the shaft from the reduction box and see whether the bolt holes line up. Thanks for the info Tony.