Mercury - Upper Water Pump Repair Kit Cooling System Marine Composite & Rubber 99157T2. Overview. There's a certain calm that settles in once you know your cooling system is moving water the way it should. Out on the water-whether you're pushing through a long channel or easing across a glass-smooth bay-you rely on that steady flow more than anything else. When the pump is healthy, the engine feels confident, strong, and ready for whatever run you've planned. That's why I lean on Mercury Marine