Your probably limited by the engine box size
Bill, I have repowered from an outboard to an inboard diesel. At the time it came down to Yanmar, or Volvo. The mechanic who did most of the work installing, was more familiar with the Volvo, so I went with a Volvo 2000, 10 hp, one cylinder. The Yanmar one cylinder I believe had a slightly bigger footprint as well. I understand Yanmar makes a 12 hp, 2 cylinder, just slightly bigger than their old 10. Gordon over on the diesel forum can confirm this. You are really limited on the physical size within the confines of the Oday 25, which was never built to house a diesel, so modifications to the cabinetry will be required. Matched with the proper prop size you may see close to theoretical hull speed at WOT, but realistically cruise at about 4.5 knots, at 70% of maximum RPM (for me about 2300), for a 10-12 hp diesel. I would bet you will have to rebuild your engine beds. I used 4"x4" oak fiberglassed in place. You may get away with keeping your prop shaft, cutlass bearing and fuel tank and throttle control, but I would confirm that with a diesel dealer. Its a big job, no mistaking that. And costly. Not for everybody. Good luck with your decisions. Don
