http://www.rbbi.com/folders/prop/propcalc.htm

two 140hp 1990 OMC. 14.5 x 24 CR 55mph @ 6200rpm (WOT) Flat seas, 40g fuel, just me on board.

Can do a lot better going with that screaming tide through the Galveston ship channel. I have clocked 70 on the gps with the tide and a 25mph wind at my back.