Need advice re. prop selection/Merc. 75 HP 4-stroke

[GANGGREEN]

I just dinged up my prop and need to purchase a new one but would like some advice on pitch, etc. I have a Fisher Hawk 160 deep V (hull weight is about 1100 pounds. The outboard, 2 passengers and 20 or so gallons of gas and equipment probably add close to 1000 pounds to the weight. The prop that I am running now is a 15 pitch 3-blade prop, I'm not sure what size. The boat's max. RPM is 4800 with this prop (this has been in relatively cool 50-65 degree weather). Mercury has a max. RPM recommendation of 4500-5500 RPM and I think that I would like to be a little closer to the top end of this range. Can anyone give me a recommendation for what prop that I need? Although I've had boats for years, I've never paid a lot of attention to things like this. I've always just had a shop replace my props when needed but I'm not convinced that I always got what I really should have had. Thanks in advance guys.

[DaveIN]

I have a Crestliner 1650 Fishhawk which is probably the same size boat with a 70 4 stroke Suzuki.
When I bought it the dealer had a 17 pitch 13 1/4 inch prop installed.
After I filled the fuel tank and loaded all my gear and my wife and I, we dropped about 800 rpm.
They gave me the same size prop with a 15 pitch and the rpm was right at the max rpm, so they took that prop and sent it in to have a slight cup set in it and that took about 300 rpm off the top end.
I know that it just takes some playing around to get it right.
Good Luck

[Kevin A]

You're over-propped. If you're running a 14-14.25 inch diameter prop I'd go down to the 13.25 to 13.5 range. Each 1/4 inch reduction in diameter will increase your rpm by around 100. If you're already in the 13.25 inch diameter range then each inch reduction in pitch will increase your rpm by 150-200. Using these numbers you'd need an 11-12 inch pitch prop...this seems really small, but I haven't run a 75hp range motor. I'm guessing you have a combo too large of diameter & too high of pitch. A 14 dia reduction to 13.25 and a reduction of 2 inches in pitch will net you out in a 13 pitch range with good rpm. Measure your current prop's diameter & go from there. By all means get the max rpm up...your lugging the motor. Remember that Hp is a function of rpm...less rpm = less Hp. You probably have a couple horses you haven't tapped. You'll be surprised how much more pep it'll have with the right prop.

[GANGGREEN]

Thanks for the advice guys, as always it is greatly appreciated.