[HeadlessNorseman]

a turbo wont help if the outdrive is the limiting factor. Thats the trans, rear, tires, and gear ratio all rolled into one. Just get a basic rebuild kit and rebuild the 305. Who cares about a warranty! Does the boat use a carb and HEI ignition? or some sort of fuel injection? It would prob benefit a lot from some fine tuning of the carb for constant throttle use. You dont really need throttle repsone or low end out of a boat motor. I would say go for used vortec heads, decent cam, and a single plane intake manifold. high 200hp at operating rpms, prob 320 at peak. Find a way to port the water jacket exhaust manifold things, or replace them. What kind of boat is it? I want to put a 50hp outboard on our boat. Its a 12ft aluminum 4 seater. Flies now with a 25hp....just imagine