Yamaha - Water Pump Repair Kit Cooling System Service 66T-W0078-00-00. Overview. A healthy water pump is one of the most important parts of keeping a Yamaha outboard running cool. The Yamaha 66T-W0078-00-00 Water Pump Repair Kit provides the core components needed to rebuild the pump assembly and restore proper cooling water flow. Over time, impellers wear down and seals harden from heat and debris moving through the system. Installing a complete kit during routine maintenance helps maintain ste