Hello all this is my first post so take it easy on me. First some background- I am actually posting trying to help a friend with his 37' Rinker. It has twin 5.7 mercruiser engines. I believe they are late 90's vintage but I'm unsure at this point. The boat is just plain under powered. It takes all the engines have got to get it up on plane. A lot of times it just wont go on plane. We've tried some different prop combos with some improvement but we're still not there.<br /><br />After looking over the engines there looks to be lots of room for improvement in the power department. These engines have multi port injection with a god awful throttle body setup and a converted carb intake manifold. being a car guy I just about laughed at the setup.<br /><br /> This is where I need some advice from you all. How similar are the mercruiser engines to chevy's run of the mill V-8's? I know nothing of boats but worlds about cars. <br /><br />My first thought was to swap to a Camaro V-8 intake manifold and throttle body. They are a much better design. They have much larger throttle bodies and intake runners along with a better intake runner/plenum arrangement. I think that should give us a little more top end power. maybe not as much as we need but it should be noticeable. Beyond that maybe put on some aftermarket aluminum heads and a performance cam. The intake manifold swap is a fairly easy job and on the cheap side. That makes us want to attack that part of the job first.<br /><br />I am very open to opinions on this.<br /><br />BTW- I assume that marine engines horsepower must be rated differently than car engines? These engines are rated at 300hp. I know there is no way that with the parts currently on the engines they can produce that kind of power. A quick bit of math shows the throttle body bores are not big enough to support that kind of power.
