I have an 18 donzi classic that I am rebuilding the engine for. The engine is a stock 260 merc and last year the boat ran 61 mph at 5000 rpm. This year I would like to run the same rpm but with a 23 inch prop. I am hoping to gain 6 mph. The question is what is the most cost effective way to make my healthy small block short block do this. I am re using my original short block and was considering the following.

As a student budget is absolutely critical

Switching to 64 cc vortec heads for 9.5 to 1 compression
Crane 272 cam
rpm manifold
stock exhaust

I have been told to spin a 23 at 5000 rpm on a classic 18 340 hp is needed. Will the above combo be sufficient?

Chris

Your stock exhaust is going to be the limiting factor. I don't think you can get to 340 hp with a stock exhaust. Give Bruce a call, (314) 952-0861, and talk it over with him.

mike