Yamaha - Water Pump Impeller Cooling System Component 6H4-44352-02-00. Overview. The impeller is one of those parts I tell people not to push their luck with. I've seen engines run fine one day and overheat the next just because an old impeller finally gave out. It's the heart of your cooling system, constantly moving water every time the motor is running. Staying ahead of it with a fresh one is just part of owning a Yamaha and keeping it reliable.. Key Features. Primary Water Pump Driver - Circulates cooling water through the engine to regulate temperature.. Flexible Blade Design - Allows consistent water flow even at varying engine speeds.. OEM-Spec Fitment - Built to Yamaha standards for proper fit and pump housing alignment.. Heat-Resistant Material - Designed to handle constant rotation and exposure to engine heat.. Preventative Maintenance Essential - Helps avoid overheating and costly engine damage.. Engine & Boat Compatibility. Designed for Yamaha outboards with compatible wate