I had the same boat back in 1989 with 4.3LX 205 horsepower. I tried at least 12 different props to get the most out of it as my bud had same boat and we were always trying to beat the other. The best prop for this boat/motor combo is a Mercury Laser II 23", leave holes unplugged. I ran it at 4800. If your only turning 4200 with a 22, you might have other issues.