I can't answer the physical questions that you mentioned above in terms of the hull, engine mounting/spacing and so forth, though I will say that your old 200 Yamaha 2 strokes weighed in the 420 lb range per outboard, depending on which model you have/had. Comparatively, the lightest 4 stroke outboards currently on the market would be Mercury, specifically the Mercury 200-225 FourStroke series. Which is 475 lbs for the lightest version, of which I'm going to assume that's for the 20" shaft version and that yours is a 25" shaft version. So, it'll probably be 10-20 lbs more per outboard on top of the 475 lb number. If you're looking for maximum horsepower then I'd go with the Mercury 225 FourStroke, especially since it's the same weight as the 200 version. The rest of the competition is going to be all over 500 lbs... the Yamaha 200/225 are going to be in the 525-550 lb range and Suzuki is going to be even heavier than that. Same goes for Honda.