prop size

[vcs]

I have a 1976 18 sf with a 1988 johnson 150. I currently have a 14.5 x 17 pitch prop on it, it is only running 5200rpm wot. I was told to go with either a 15 x 19 or 15 x 21 prop any suggestions.
Tony

[Bushwacker]

You were told wrong! If you want more rpm, you need LESS diameter or pitch, or raise motor 1 hole (cavitation plate can be about 1" above bottom of boat if you run a cupped prop). I tried 14.5 x 19 and 14.25 x 17 stainless props; the 17" pitch prop picked up 200-300 rpm. Currently running a 14 1/8 x 20 4 blade SS, but it's a little too much for heavy load. Am considering having Bobby Soles cut it down some. He's a good source of prop info and also sells used props.

[PipeDreamsMarine]

leave it the way it is.. Your only 300rpm off what it should be. With a motor that old and your only 300 off .. your doing fine..

[76Red18]

I HAVE AN 18 WITH A 99 150, T TOP , 15 X 19 STAINLESS, 42MPH @5500