Mercury - Water Pump Impeller Repair Kit For 8 & 9.9HP FourStroke BigFoot/Command Thrust 803748K02. Overview. Your engine's cooling system is the heart of its reliability, and the Mercury Marine 803748K02 Water Pump Impeller Repair Kit keeps it running perfectly. Designed for Mercury 8HP and 9.9HP FourStroke outboards equipped with BigFoot or Command Thrust gearcases (model year 2005 and newer), this OEM kit includes everything you need to restore proper water flow and cooling performance. It's