A variable-capacity water pump includes a housing having an impeller mounted on a rotatable shaft. The impeller includes a plurality of vanes pivotally coupled between upper and lower shroud and operatively coupled to a pitch plate. As the pump speed increases in response to increasing engine speed, the pitch plate controls the rotation of the impeller vanes about a fixed rivet from a maximum pitch position, toward a minimum pitch position, thereby lowering pump output according to engine cooling requirements.