Joe Kriz wrote:
Any motor needs to run within the manufacturers suggested range.

What are the RPM's of the engine at WOT?
You should be within the range of engine specs.
Many engines have a max RPM at WOT of around 5k to 6k as a example.

A prop is selected by the above along with a few other things like a bow lifting prop, stern lifting, etc.... However, the max operating RPM's must still fall within the manufacturers suggested range.
Otherwise, you will be under-propping or over-propping your motor and that isn't good and could cause damage, excessive wear, poor performance, and possibly vibrations.