Just curios, are you looking for a nitro outboard or electric for you scale model? I would think electric would be far easier to make look like a scale outboard. Outboard nitro's used to be available in 3.5, 7.5 & 11 cc sizes, I think OS engines has outboards, but I'm not sure what else available now. I actually have an old K&B 3.5 cc outboard, it hasn't ever seen the water except in a bath tub, when i was younger to just run it for the heck of it, boy was that a mess. One day, i will get back to it.

3-view drawing, are you having a problem obtaining the drawings for the outboard or the hull. If you looking for the outboard drawings, you can always try your Yamaha mechanic, i'm sure their maintence manuals have some form of drawings, ask if you can xerox.