JaxJonBoat
Well-known member
ok not to bring up an old topic but I have a question that I cannot seem to be sure of. I think I need to go down a pitch on my prop. I am running 5450 RPM at WOT with just me in the boat at around 18.5mph and around 5200 with another person in the boat. I have a 1987 Johnson 9.9 with a 15hp carb and it has the stock 10" pitch prop on it and I know the 9.9 and 15 came with the exact same prop as OEM. The RPM range for a 15 is 5500 to 6500 and for a 9.9 is 4500 to 5500 i believe. My question is this.....I need to get my RPMs up solid into the range for a 15 and I am thinking that going to a 9" pitch SS prop would do the trick BUT would the extra efficiency of the SS prop put more load on the motor and lower the RPMs because it would have less slip and actually move more water? I always hear that a SS prop gives you a little more RPMs compared to an aluminum one because of the thinner blades but the whole less slip thing got me wondering and second guessing myself. I just would hate to spend the money on a prop and it be the wrong one and I do not know anyone that I can borrow one to test. I know I am probably way over thinking this but it has been bugging me all day.