Mercury - Inlet Water Hose for MerCruiser MR, Alpha One and Gen II Transoms Cooling System Component Molded Marine Rubber 8M0215001. Overview. There's a certain confidence that comes from knowing your engine is getting the cooling water it needs, especially when the afternoon sun is beating down and you're running across choppy water with a full boat. The inlet water hose might not look like much at first glance, but it plays an important role in keeping your MerCruiser drive healthy and steady.