Last year I dropped a new motor in my boat. Not my choice but it had to be done, long story so I won't go into it. Boat is a 2000 glastron/Carlson CSX21 it had a Volvo 350 280 HP with a SX outdrive 1.43 ratio and I had a carbureted ZZ383 425 hp and 450 Lb ft torque installed exhaust is thru motor not thru hull. This is where it gets interesting. currently have 19 pitch prop turn 4800-4900 RPM - 50 MPH at elevation 4900 ft (pineview reservoir Utah) at Lake Mead same prop 5000 RPM 60 MPH at elevation 1140 FT.
Shouldn't I be turning more RPM's at Lake Mead? Maybe my gauge is messed up.
Is the gear ratio the issue at higher elevation?
I should be running around 5500 RPM at WOT or more
Do I need to pitch down to 17?
Suggestions, input or ideas?