Mercury - Quicksilver Water Pump Base Assembly Cooling System Part Reinforced Nylon 48748A1. Overview. If your MerCruiser is running hotter than normal or losing water pressure, the problem might start at the pump base. The Mercury Marine 48748A1 Quicksilver Water Pump Base Assembly gives your cooling system a solid foundation, keeping the impeller aligned and water flowing smoothly. Designed for MerCruiser 120, 140, and 160 sterndrives with flush screw-in gear housings, it's made from reinforce