Originally posted by thewavehumper
that's the fella, I think it might be more appropriately called a power transfer plate, It's a big steel soup bowl, with a rubber insert which is about 10 inches in diameter this is made of Rubber and has what appears to be spring steel inside the rubber
The problem now is deciding if it's a "Cat" part or a Hamilton Jet part. You could try phoning Hamilton on Ph: 01342 313 437, their based in west sussex and I've always found them very helpful.
It may also be worth talking to Lancing Marine, Mike used to sell Hamilton jets (might have been Castoldi) and he seems to know quite a bit about them. It's quite possible that he stocks the part you require, as it won't actually be made by either Cat or Hamilton!