Finally fixed, RPM's still low
 

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 ?

good to hear you found the problem, Thats why I suggested separating the harness from the engine. have you checked your tach against another one?

No, I'm not sure the best way to check. I have asked what the normal idle RPM for my motor is and Was told by users on this forum it should be around 700-900 which is what I have. Could my tach still be bad? do my speed and RPM numbers sound like they are on track ( 30 MPH @ 4000 )?

went out today, ran good, I was alone with no gear and 20 Gall. fuel, got it up to 4300 RPM's 32 MPH going with the tide, light wind, trimmed up all the way.

are you using a gps for speed?

Yes, it's an older handheld