I think 'saildrive attached' might also mean just a clutch and in/out/reverse transmission attached. I've seen a few like that on ebay. The manifolds and cooling would likely be different from a tractor engine.
Also, I think the 2Q series of Yanmar boat diesels from the 1970's are the same block as the 2TR20 engine in the YM2000 tractor. I've wondered if the overhaul kits, injectors, etc are the same. Does anyone know?