Is there a modified formula for power valve tuning a jet boat as compared to a car? My original Holley came with a 2.5". It makes sense that it would be lower than a car application because jet boats are run at full throttle much of the time. My Marine Demon came stock with a 6.5". It is a pain on the ass to remove and drain the magnum fuel bowls for tuning purposes, so I'd like to take out as much of the guess work as possible. The engine is a 320 HP Vortec 5.7 with a "Ramjet" cam. Its duration is 288/308; duration at .050" lift (intake/exhaust) is 196/206 and maximum lift is (intake/exhaust) is 431/451. Lobe centerline is 109 degrees. I'm running an American Turbine SD-309 pump with an "A" impeller in a 20' Eagle aluminum bass boat.