can anyone help identify this part

[Davef]

Hi
I have a volvo penta with MS2 gearbox, this green 'biscuit tin' sits between the drive shaft and the gearbox flanges, does anyone have any idea what it is ? I thought it could be some sort of flexible coupling but the whole thing appears solid ?/

 

[Oldhairy]

Could it be a vibration damper?

 

[Avocet]

It could well be something that doesn't take up misalignment, but takes up (or is supposed to take up!) torsional vibrations. If it's the latter, it will be a series of interlocking fingers on each side of the joint, with rubber cushions inserted into the gaps between them. Useful for going from ahead to astern or even when engaging gear, just to cushion the instantaneous shock going down the propeller shaft. The rubber is often pretty hard to start with, and will have lost some elasticity with age too. (Of course, it could just be some sort of rigid adapter, simply because the back of the gearbox was too far from the nose of the propeller shaft)!

 

[saxonpirate]

It could well be something that doesn't take up misalignment, but takes up (or is supposed to take up!) torsional vibrations. If it's the latter, it will be a series of interlocking fingers on each side of the joint, with rubber cushions inserted into the gaps between them. Useful for going from ahead to astern or even when engaging gear, just to cushion the instantaneous shock going down the propeller shaft. The rubber is often pretty hard to start with, and will have lost some elasticity with age too. (Of course, it could just be some sort of rigid adapter, simply because the back of the gearbox was too far from the nose of the propeller shaft)!

There's not a lot else it could be, and Avocet seems to have covered all the options. I had an MS2 box on my last boat and there was a solid metal spacer about half the size of your fitting bolted to the shaft when I bought it. I removed it and fitted a flexible coupling.

Is that just a metal shroud covering a rubber flexible coupling? What does it sound like if you tap it with a small hammer?

 

[KenMcCulloch]

It is a rather old semi-flexible coupling. We have an identical one on the back of our Bukh. If you undo the four long bolts in the periphery of the cylinder you will be able to separate the housing from the plate which is bolted to the gearbox flange. That will give you access to inspect the condition of the rubber bits that provide the flexibility. When we had to take ours apart recently I was surprised to see the rubber in such good condition given that it is probably original and therfore 30 years old.

 

[Davef]

It is a rather old semi-flexible coupling. We have an identical one on the back of our Bukh. If you undo the four long bolts in the periphery of the cylinder you will be able to separate the housing from the plate which is bolted to the gearbox flange. That will give you access to inspect the condition of the rubber bits that provide the flexibility. When we had to take ours apart recently I was surprised to see the rubber in such good condition given that it is probably original and therfore 30 years old.

Great Thanks everyone for your comments, Ken that explains it really well, I assumed it was some sort of flexible coupling, I will take it of to examine at the weekend to answer the previous post its a fairly substantial case and sounds fairly solid when tapped. since running over a plastic bag late last year I have little power under drive and I am trying to identify whats causing this and thought that this green box may be the problem! looks like I will be replacing it with a new flex coupling and some clever engineering 'in fill' to extend the shaft the missing amount.

 

[Davef]

Thanks all for your expert opinions i will be removing it on Saturday