Finally fixed, RPM's still low

[Joker2]

Finally fixed motor, when the mechanic gave me a newer control box he spliced my harness and did a crappy job. The bl/ yw kill circuit wire was exposed int three spots and so was the yw / rd power wire. redid the whole thing " the right way " she runs better than ever real smooth, no shaking. I am still only getting 4-4200 RPM's though. Speed is 29-31 MPH at 4000. Prop is 15-1/2 X 15 Alum. she jumps onto plane. I can get a hold of a SS 14 X 19. My friend has this on his 21' Hydra Sports ( heavier than mine )with an 89' 200HP Evinrude on a gil bracket, he gets 6,000 RPM's sometimes more, and his boat is FAST ! not sure exactly the speed but it has to be around 45. Do you think this will make up the difference? Will it be a dog out of the hole? Also the mechanic told me when I bought the motor that he put on a lower unit that was a newer year than the 94' motor, could the gearing be different in the lower unit ?