How does the prop size affect RPM's. I want to get some more speed out of my boat if possible. I have a 17' Bayliner V Hull fish and ski with a 1986 85 hp force on it. The only reference number I can find on the prop is a series of numbers that are all but unreadable X 17. I am assuming that this is a 17 pitch prop. The prop has seen some use and could use a rebuild as soon as the summer is over. At the present I get about 30 mph at 4500 rpms, at WOT it runs about 32 at 4800 rpms. Also, what are safe rpms for this engine, the engine starts and runs like a dream.
<br /><br />At sea level and a good motor you will probably use a 13.5 and 17 pitch and get about 32-35 mph if unloaded.<br /><br />I used a 15 and got 30 unloded but was at 4800Ft and have the wrong jets. And only getting 4600 rpm too.<br /><br />Will do a tear down this winter of all three carbs. Surpirisingly enough the bolw that I say looked clean even though it was sitting for almost a year. Gotta give the Stabil a hand!