Pontoon Boat & Deck Boat Forum

I just bought a 1996 Harris Omni 20 cruiser with a 40 Evinrude. Never had anything like this so I have had it out on the water and it runs perfect accept when I get to about 3/4 throttle and it seems like the prop loses contact, is this cavitation? Still turning same rpm but it losses thrust and slows down and then starts thrust again? I am moving at a pretty good clip and creating a good size wake. I have adjusted trim and that helped get to a little higher speed but at some point it still losses thrust.
What should I be expecting out of a 20' 40ph in rpm and speed?
Thanks

Welcome ! Sounds like cavitation to me. I wouldn't expect more than 15 mph with just one person aboard, a few mph less with each added passenger.