2004 215 Weekender 5.0L 220 HP. I have the boat 3 years, came with a 14x19 SS prop on the boat. I'm maxing out at 4200 WOT pushing it to get up to 26 MPH. It used to go faster but the last month of so it slowed up. I used to cruise at 26 MPH and top speed of around 32.The engine's running good, just not moving like it was. I changed the prop to the original aluminum 15x17. I can now get 4800 RPM's at 28 MPH. harder to get on plane. 3500-4000 RPM's. With the SS prop getting on plane was a piece of cake, under 3000 RPM's.I feel with the aluminum 15x17 it's just pushing the engine too hard so I'm going back to the SS 14x19 for now. I'm stumped. any suggestions?