Mercury - Water Pump Impeller Cooling System Component Fiberglass-Reinforced Insert 89984T3. Overview. Keeping an engine cool is one of those things you never think about until it stops working the way it should. Whether you're running an older sterndrive, a classic Mercury outboard, or a dependable Mariner setup, steady water flow is what keeps you moving without worry. The Quicksilver 89984T3 Water Pump Impeller brings that confidence back. It's the kind of part you install once and immediatel