The 21 prop is spun by a 1999 Evinrude 225 High Output, reportedly closer to 250 hp than 225. I think this motor was designed for bass boats with 225 transom ratings. I can get the V20 to about 57 mph on GPS without too much weight in the boat. I cruise at 40 at 4400 rpm's. If I trim it just right, I can get 3 mpg as well.