I had a 1991 17ft Glastron with the 4.3LX (4-barrel) 180hp motor. Somewhat like your boat. The best all around prop for that boat was a 21" QSS Mercury Quicksilver prop. It turned 4800-5000 RPM at 57mph (on GPS). A Mirage Plus 21" might be a good choice too. It might be a little more expensive though.