A pump (10) includes a housing, a stator (20) supported in the housing, and a rotor assembly (30). The rotor assembly (30) includes a rotor (32) supported in the housing for rotation relative to the stator (20) about an axis (12). The rotor assembly (30) also includes a first impeller (34) operatively coupled to a first axial end of the rotor (32) for rotation with the rotor about the axis (12). The rotor assembly further includes a second impeller (36) operatively coupled to a second axial end of the rotor (32), opposite the first axial end, for rotation with the rotor about the axis (12). The rotor assembly (30) is movable along the axis (12) relative to the housing to adjust hydraulic performance characteristics of the pump (10).