I recently bought a boat
with a Max-prop that was badly overpitched. Fortunately, the owner's manual specified the pitch. If you do not have that information, the definitive text on the subject is "Propeller Handbook" by Dave Gerr. The formulas can be intimidating, though. After that, you have to determine your current
pitch and how to change it.
Short of all that, you can probably estimate if you are pitched correctly. If you motor
close to hull speed
at 80-85% of your engine's maximum RPM
, you are probably about right. If you start belching black smoke at or before you reach 85% of max RPM, you may be overpitched (provided your prop and bottom are clean). On the other hand, if you cannot get close to hull speed
in flat water
at close to your engine's max RPM, you may be underpitched. Or you may have insufficient horsepower or too small a prop (in surface area/# of blades).
In my case, I had smoke at 50-60% of the max RPM with a clean hull
and prop. I also was moving at 3.5 knots at idle. After taking about 4" of pitch off, I'm still a touch overpropped but I can run at about 80-85% of max RPM without smoke.