I run some of my boats with a gravity feed fuel system. The Mean Green and Tylers boat are both gravity fed,along with the 108 boat, and another one of my brothers.

Gravity fed meaning that the fuel tank sits at the carb level or slightly above it about a 1/4", I also run the shortest fuel line possible to the carb. This allows the fuel to get to the carb without any pressure from the motor. Which allows you to take out the baffle or do like I do and remove the entire exhaust tip.
This give you an open header!!!!! Now the engine has no back pressure, which will allow it to turn up the rpm's quicker and doesn't take as much hp to get its fuel.....she becomes pretty "peppy"!!!! I set the needle valve like you would any other set up.
And from my experiments I get better engine performance and fuel economy from this set up. The only down side to this set up is you give up a little bit of initial response from an idle to acceleration (not enough to make a difference),and its a little louder. But then again I don't idle my boats ever...they were built to run and that's what I do with them! I run 'em like I stole 'em!!!!!!! (Please don't take me for a thief....its just a metaphoric phrase.)

I have experimented with the set up quit a bit. I run a conventional set up on 3 boats a 46FX, 46LA, and a Magnum 108. Then I converted them to gravity feed and the response was better with the gravity. I haven't used a tach on the two set ups but just by running them I can see a difference. And another thing....it costs you exactly $0.00!!!!!!

Check out the video footage on my web page and you can see how the gravity fed motors run.

It's late and I gotta work tomorrow. Any questions or comments?...I'll be more specific if anyone has any questions.