Yamaha - Water Pump Repair Kit Cooling System Service 6H4-W0078-A0-00. Overview. If you've run Yamahas long enough, you know the water pump is one of those things you don't ignore. This kit is what you reach for when your telltale stream weakens or you're doing preventative maintenance before it becomes a problem. It's built to bring your cooling system back to proper flow and keep your motor running at the temperature it was designed for. Whether you're in salt or fresh water, this is a routine