I would have to agree with MikeL on the prop selections and getting yourself some test props. But if you really want to get scientific, along with the multitude of props to test based on the manufacturers recommendations, get a tachometer. This will help to find the maximum safe range for your engine.

I'd hate for you to go beyond the RPM range and burn-up/seize your engine. Yeah, the ears work, but if you have a 4-stroke, forget it! It’s generally harder to tune a 4-stroke compared to a 2-stroke, unless of course you have years of experience with a 4-stroke or have seized enough of those to know better.

My 4 cents…