A pump assembly includes a base plate upon which a drive motor is mounted and pump plate upon which first and second pumps are mounted. The pump plate is adjustably mounted on the base plate so as to be moveable between first and second positions relative to the base plate. In the first position, the first pump is operatively engaged with the motor and the second pump is disengaged from the motor. In the second position, the second pump is operatively engaged with the motor and the first pump is disengaged from the motor. An operator can quickly and easily change from one pump to the other simply by loosening thumbnuts, repositioning the pump plate on the base plate, and tightening the nuts.