Mercury - Water Pump Repair Kit Cooling System Rebuild Multi-Piece OEM Kit 89983T1. Overview. Keeping a mid-range Mercury outboard running cool isn't just about performance - it's about trust. When you're pushing through a shallow creek, drifting a river mouth, or cruising across the lake, you're counting on that outboard to stay steady and dependable. Over time, though, sand, silt, and fine debris slowly wear away the inner surfaces of the water pump. That's when you start to notice a weaker te