[oldfielder]

Since there are a lot of 23 cc's with o/b here, I can chime in and say that my i/o's top end has been around 41 mph burning about 20 gph. My optimal cruise is right around 27-28 mph, getting 2.8 mpg. This is with a mercruiser 250/carbed/alpha.
It does ride like a tank when i need it to. The funny thing about fishing space on this boat is that I fish most often with two guys and the engine compartment makes an excellent casting platform in the back.