150 HP Evinrude not reaching RPM´S

Hi everyone!

I just bought a Champion 18´6 bass boat With a 1993 150 HP Evinrude Ocean Runner (20" gear case) seated on a 6" jack plate with a 14-1/4 x 23 Alumunium propeller.

The compression test result was 115-120 lb on each cylinder.

The hole shot is excellent ,but the top speed is just 45-47 MPH and just reach 4700 RPm´s

Where should I Start to make changes to reach 5400-5500 RPMS and increase my MPH??

I did Rise the motor with the jack plate 2" but I did not perceived substantial changes
.
Thanks in advance.

Sounds like you are running on 5 cylinders. Verify you have spark on all plugs at ALL rpms. If so, then move to the fuel side. If this is a carbureted motor, i’d say check all your main jets and make sure you don’t have a blockage somewhere.