The information I have was supplied by Richard Bartlett. A company called Countrose (www.countrose.com) in Birmingham make all bearings for many boats and I think supply Nauticat. The size bearing for the 331 is 55x40x160mm with a brass casing part No CRM009. Also I believe the same size for the 33 and the 42 possibly others. Speak to Nauticat? They are made of either Nitrile or Polythene rubber. Nitrile is softer and accommodates shaft out of alignment. Polythene is harder and wears much better. Richard said he has used a polythene version for 14 years without any apparent wear. I have obtained one from them and as I live close by went and collected it from the factory. I have yet to fit it but will be doing so soon. Richard also gave me the following info.
1. Take an old 40mm Dia cutlass bearing and cut it in half long ways.
2. Cut out the rubber completely.
3. Clamp the shells onto engine side of shaft with 2 jubilee clips.
4. Using 2sash type clamps use shells to push cutlass bearing out of P bracket
If you remove prop first and then reverse the procedure to put new bearing in.
I hope this is of some help.
Paul (Dotecom) Marina de Portimao, Portimao, Algarve Portugal.