Hi Sgt. Pluck, I have just read about your experiences with your M-25XPB. I installed the same motor last year, and have had two transmissions go, same as you, in under 300 hours total. I also find that the damper plate is damaged, with the teeth in the socket worn to about 50%.
How did you rectify the problem? I am negotiating with Westerbeke under warranty, but am a bit isolated, stuck in the Marshall Islands until I can get the motor running again.
I would appreciate any advice; sounds like you've been down the exact same route.