I'm not sure what the exact number of degrees is, but I do know that the important part is that the pump shaft and the crank stay parallel. If the driveshaft has an equal deflection at the beginning and the end, the vibration will cancel itself out, and you will have no problems. If it is not equal, for example the motor is tilted going into the pump... you will have major vibration occur, and the drive will shake itself apart.
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