Mercury - Water Pump Impeller Yamaha 4.2L Cooling System Marine-Grade Polymer 8M6010334. Overview. Every boater knows the sound of an engine that's running just right-the steady hum, the smooth push, the subtle confidence that tells you everything below the deck is doing its job. The Quicksilver 8M6010334 Water Pump Impeller is one of the quiet heroes behind that feeling. On powerful 4.2L Yamaha 200-300hp outboards, cooling isn't optional-it's essential. This impeller keeps that cooling system a