Prop Selection for 1995 force 40 hp

[Clhart22]

Hello all. This is my first post on iboats. I have a 1995 force 40 hp outboard on a 15x42 aluminum boat and I currently have a 14 pitch prop on it. It gets excellent hole shot but top end could be better (only 29 mph down river). What prop would be a better choice?

 

[SkiDad]

I'm guessing you don't have a tach? Without that you can only guess. 29 seems good to me. You could try a 15 or 16 but you will only gain maybe 2 mph.

It would be good to get a shop tach to take with you to see where your rpms are at.

They need to be at least 4800 or you will be out of range. But no more than 5300

 

[Scott Danforth]

what RPM are you spinning?

I assume that the 29mph is per a GPS and not a pitot tube speedometer, correct.

Using Mercurys prop calculator, inputting in your 2:1 ratio, a 14 pitch prop, 15% slip and 29 MPH, I calculate 5147 RPM. which is right where you should be

I dont think you have a problem. if you want to go faster than what the motor is designed to do, you need more motor. and on your 15x42 boat, your probably already maxed out on rated power

Motor Specs
Manufacturer: Force
Year: 1995
Horsepower: 40.0
Cylinders: 2
Type: 2 stroke
Gear Ratio: 2.00:1
Min WOT RPM: 4750
Max WOT RPM: 5250
Spline Count: 13