I've done some research on various engine replacement options for when the time comes. None of the diesels that have enough power will come close to fitting in my 425, even ignoring the question of where to put the radiator. The Robin engine is particularly compact front-to-back. IIRC, it's just over 13" from the fan end to the opposite flange. It looks like the whole engine/pump assembly could be move forward a couple of inches, but the diesels are a good bit longer than that. I figured that I'd have to lengthen the tub by 6-12", depending on the engine.
I have seen photos of a Chinese v-twin air-cooled diesel that looks like it would fit and should be in the ballpark for power, but it doesn't appear that it is actually being imported.
I think the best bet would be the new big-block Kohlers. They are rated at upwards of 30hp, and are rated for something like 25 degrees of tilt. The big Generac that PT prototyped is only rated for something like 15 degrees, and seems to be unobtainium anyway.
I'm going to hope that my Robin holds out until something really greatcomes along...
Gravy
