Yamaha - Water Pump Assembly Engine Cooling System YF1-43847-30-30. Overview. If there's one part you don't want failing on the water, it's the water pump. I've seen Yamaha engines go from running perfectly to overheating fast when the pump stops doing its job. The Yamaha Water Pump Assembly YF1-43847-30-30 keeps coolant moving through the engine so temperatures stay where they should. It's one of those components you trust every time you start the motor, whether you're cruising or pushing it ha