I thought I'd add this link to the thread since it seems relevant. 350's are so cheap . . . it seem like it'd be really easy to put together a decent motor for short money. Carbs are so simple and clean that it seems like that's the way (in a boat) to go vs. fuel injection.
http://www.offshoreonly.com/forums/g...062-906-a.html
Post from "Kornegle"
" I have posted a similar reply before, but I purchased the standard Vortec castings from Summit Racing not the ones with Iconel. I removed the stock heads from a 1990 / 91 Mercruiser 260. Kept the same pistions, installed the Vortecs, an Edelbrock Performer manifold, 1.5 roller Rockers, XM256 cam, Outer Z28 valve springs, new Mercruiser manifolds and risers. This is a heavy 3300+lb Wellcraft Eclipse 21 1/2 ft. Cuddy. Before mods, ran about 52.7 on GPS with a Mirage 21P. After mods turned a Mirage 23P at 5000 - 5100 rpm and 60.3 on GPS (a lot of propeller slip on this antique hull). So all these mods together picked up around 7 mph. I can only estimate that might be 300 propshaft HP from the previous 230 propshaft HP, but only a guess. There is a bit more in it with the right prop. "