What part of the US are you in? Where do you normally run?
On the Pacific coast, it's rare when you can run flat out without beating the crap out of yourself and your passengers (picture stuff and people flying out of the boat while bouncing off the wavetops.)
On lakes it's a different story, of course. Lighten the boat (should yield a little speed), reprop for more pitch (assuming you're not getting full rpm), get a bigger motor (won't get you as much as you'd think.)
Oh, and if you believe the kids on the street in the Hondas, a big exhaust pipe and a little wing on the back.