I have a 78' 23 CC with a pair of mid 80's crossflow omc 150's with 21 pitch props it tops out at 50mph at 5200 rpm and cruises at mid 30's and gets a wopping 1.25 mpg. I am currently rebuilding a omc 225 to replace the 150's and also will be running a 25hp omc for a kicker. Hopefully this will increase my fuel economy without losing to much performance.