How can one tell if a damper / drive plate is knackered?

[jdc]

My boat's transmission has been chattering at low revs for a couple of years, and getting worse. Last winter I replaced the Gori 3-blade prop in case that was the cause (Silette-Sonic said it was marginal and not really worth sending back to Denmark for refurbishment) but it made no difference. The revs at idle are definitely above 800rpm, and it makes no difference whether in forward or reverse.

The engine is a Beta 50HP (Kubota 2203 based) and the gearbox a Hurth ZF 25. ~3500 hrs on the clock, and I mostly run it at low revs. Beta told me that R&D were the best source of dampers now, so I bought a new damper plate from R&D - who were very helpful - and have just fitted it, taking out the old one, which I have here.

It is quite different to the Borg-Warner ones I have seen before, so I'm wondering whether it is in fact knackered. I believe (from Google images) that it's a Centa one - see pics - but don't actually know this for sure. The two parts can be rotated by hand between the rubber stops with very little force, which seems wrong, but nothing was obviously awry apart from this - some small bits of rubber in the flywheel case, but not a great deal, and no signs of scoring etc.



I guess the proof will be on running the engine with the new R&D one, but that won't be until April and it would be good to know if I should search for some other cause while the boat is ashore. Does anyone have experience with this type of plate (and is it indeed a Centa one?

 

[john_morris_uk]

How much play was in the bearings of the gearbox input shaft?

 

[Boater Sam]

Looks well worn to me. The R&D one will be quieter.

 

[jdc]

How much play was in the bearings of the gearbox input shaft?

None (or, at least, so little I couldn't detect any).

 

[Plum]

My boat's transmission has been chattering at low revs for a couple of years, and getting worse. Last winter I replaced the Gori 3-blade prop in case that was the cause (Silette-Sonic said it was marginal and not really worth sending back to Denmark for refurbishment) but it made no difference. The revs at idle are definitely above 800rpm, and it makes no difference whether in forward or reverse.

The engine is a Beta 50HP (Kubota 2203 based) and the gearbox a Hurth ZF 25. ~3500 hrs on the clock, and I mostly run it at low revs. Beta told me that R&D were the best source of dampers now, so I bought a new damper plate from R&D - who were very helpful - and have just fitted it, taking out the old one, which I have here.

It is quite different to the Borg-Warner ones I have seen before, so I'm wondering whether it is in fact knackered. I believe (from Google images) that it's a Centa one - see pics - but don't actually know this for sure. The two parts can be rotated by hand between the rubber stops with very little force, which seems wrong, but nothing was obviously awry apart from this - some small bits of rubber in the flywheel case, but not a great deal, and no signs of scoring etc.

View attachment 169359

I guess the proof will be on running the engine with the new R&D one, but that won't be until April and it would be good to know if I should search for some other cause while the boat is ashore. Does anyone have experience with this type of plate (and is it indeed a Centa one?

If you can easily rotate the two parts by hand from stop to stop then it has no damping effect so not doing what it is supposed to do.

 

[jdc]

yes, but did it ever?

 

[jdc]

Many thanks to those who replied: I agree that it is indeed knackered! I took off the giant circlip this morning, and saw that the rubber inner is broken into many small shreds. I still don't know the manufacturer, but feel its quality wasn't that good so I'm glad not to have bought the same.

 

[Plum]

Many thanks to those who replied: I agree that it is indeed knackered! I took off the giant circlip this morning, and saw that the rubber inner is broken into many small shreds. I still don't know the manufacturer, but feel its quality wasn't that good so I'm glad not to have bought the same.

View attachment 169418

thanks for the feedback. Looks like a Centa damper

 

[fisherman]

This is probably unhelpful. Chap had a PRM box, and cut his tickover down as low as possible. The oil pump drive was a flat blade in a slot and it chattered until it sheared. You never know.....