Mercury - Water Pump Pulley MerCruiser Sterndrive & Inboard Series Steel, EDP Finish 8M0150724. Overview. Anyone who's spent enough hours behind the helm knows how much trust we place in the little things-the parts we rarely see but depend on every moment we're underway. A water pump pulley might not be the star of the show, but when it's doing its job, everything feels right: the engine stays cool, the power stays steady, and you can focus on the water instead of worrying about what's happening