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kyflshooter

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ok 1st I am running a 1648 cc has a 1976 75hp omc , motor came with a 21pitch ss prop, rpms at wot where only 4800 and top speed was 35mph per gps, so I tried a buddys 17 pitch and rpms got up to 5500 but top speed was 34- 35 mph, want to try a 19 pitch also motor is 1.5 inches high as well any suggestions would be appreciated
 
A 75 on a 1648 seems way too big. Max rating on that boat is probably only 50hp.
However if you're saying the motors cavitation plate is 1.5" above the bottom of the boat hull, you may need to lower the motor.
 
RPM-wise the 17 is the way to go. That engine was never known for its bottom end power so you will lose planning power by going back up in pitch.
Typically that particular engine needs to run upward of 6000RPM.
Try different 17" propellers. There are many manufacturers.
 

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