Indmar 5.7 310 HP, What is the best carb to run on the set up.

[Walt T]

This is obviously not set up correctly, we don't have enough or the correct information and the OP isn't an expert so between all of us there's missing information, wrong assumptions, pretty much poor communication. You still have to verify the carburetors set up and linkage. There are so many reasons a boat motor (s) wont reach WOT rpm and it's been listed in the adults only section. I suspect you have something overlooked.