http://www.classicseacraft.com/commu...50&postcount=9
A 90 should be fine. I have that Yamadog 100 (90) hp 4 stroke. It is fine. I think the corrosion resistance of something better than a Nissan/Tohatsu or a Suzuki would be preferable to me.
5MPG. Because of that, I run a 20 gallon tank, although 30 might be nicer.