Mercury - Water Pump Impeller Yamaha Cooling System Marine-Grade Rubber 8M6010331. Overview. Anyone who runs a small Yamaha outboard knows the sound you never want to hear-the sputter that hints your engine is getting hotter than it should. A dependable impeller is one of those little things that keeps you boating with confidence. The Quicksilver 8M6010331 Water Pump Impeller gives your Yamaha 25hp C25 outboard the steady water flow it needs to stay cool, whether you're easing through a no-wake