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Problem , need help
2003 ZX225 with a HPDI 225 motor. Boat ran great for 16 years. 66-70 mph in good water at 5800 rpms. Never once hit the rev limiter. Motor finally died and I got a remanufactured powerhead, changed everything over, followed break in procedure it now I can only get 50-55 mph running at close to 5600 rpms. Have a lot of pedal left and I know I could get more speed but I’m sure it would be spinning around 7000and I don’t want to blow the new one. I didn’t change anything in the set up. Running the same VMax 25 prop as before. Any suggestions as to why it is so different than before. Any help would be greatly appreciated. The only thing I have not done yet is clear the codes from the old motor. Speed is through GPS.
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Those numbers do not add up mathematically. An rpm is an rpm from the drive shaft to the prop no matter what is making the rpm. According to the numbers given you are having way more prop slip with the new powerhead, and that doesn't make logical sense with everything else being the same (unless new powerhead was significantly different in weight). I would make sure your tach and method of measuring speed are both reading accurately.
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Check your tach, making sure its accurate.
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I agree, there is something wrong with the tach.
Make the mechanic that did the motor, check the tach against
his computer readout. I would assume that you got a new ignition in that package.
Your tach may be out of date with the new package.
And if I read the newer manuals correctly, the ecm would not allow it over the rev limit.
Good Luck!
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