I run a Turning Point Express Mach4 19P stainless prop. Motor is still in the 2nd hole down (where it came from the factory). I can turn it 5800+ RPMs day long at 46 mph or so. Speed is via GPS on Humminbird and RPMs are via Vessel View mobile. I need to raise the motor another hole because while I can turn nearly 6k RPMs, I stop gaining speed around 5600 or so.