I am new to owning a boat & new to the forum. I need advice on my engine & stern drive. The boat I bought has a 350 engine in it & a Volvo penta sx 1.6 outdrive & a 17 1/4 x 21 prop 3 blade. The boat is a 1997 Four Winns Horizon RX. My question is at cruising speed it’s at 4000 rpm’s & that’s only at 20mph. This seems very high. With the boat loaded with 6 people it takes 4500-5000 rpm’s just to get on plane & at least 3 people have to sit in the front. Any suggestions or help would be greatly appreciated.