As kamenges said, setting the drive parameter for 75hz on a 60hz motor will starve the motor for voltage over its whole operating range. The result will be less torque so, yes, that may well be the reason that the pump couldn't "keep up".
If, at full speed, you have surplus hp, you can run the motor and pump overspeed as long as the pump is rated for that. Simply set the max drive speed (or hertz) and the max speed reference speed (or hertz) higher than 60hz. Take this in little steps because the motor will run out of hp at some speed and then you can't go any farther.
In any case, the entry for motor nameplate frequency must stay at 60hz.