Ok guys I am running a 14 ft john boat with a 22 hp predator engine with a 7x4 prop on a go devil frame. I am only running 8mph loaded and basically the same unloaded with just me in the boat with a 6 gallon tank and battery. What size prop do I need to be running. I see 16 ft boats on you tube same set up that are running in the upper teens to lower 20s. Any help would be appreciated thanks.

I've got a 23hp vanguard on a 1438 jon and I run a 9x5 and get the right rpms. You could probably run that. At peak rpms I'll see just over 17mph.