Solas Amita prop prices make it affordable to try different props to optimize your gas mileage, I can buy one for around the price of 1 fillup.
Lets face it, fuel is your biggest reoccurring expense to running your boat, at around $4 dollars a gallon for dockside ethanol free.
Higher pitch=better gas mileage.
I run the highest pitch the motor will pull and adjust the diameter of the prop to keep the rpm towards the lower end of the wide open throttle range when fully loaded with fuel etc.
17-19 pitch on 2 strokes.
21-23 pitch on 4 strokes
Larger diameter reduces rpm.
Smaller diameter increases rpm.
Having owned 6 boats with 70, 85, 90, 110, 115 and 135hp engines, half 2 stroke and half 4 stroke, I have learned alot on prop selection.
4 strokes should use a 4 blade prop. They have the torque to turn them, 4 blades really start to hook up at 3500-4000rpm, right in the torque band of a 4 stroke.
2 strokes should use a 3 blade prop. They don't make torque in lower or midrange rpm's
3 blade props really start to hook up at 5000rpm range, where a 2 stroke is at the beginning of its powerband.
1/4" of diameter=approx 150-200 rpm at W.O.T
1 degree of pitch=approx 200-250rpm at W.O.T