Yamaha - Thermostat Engine Cooling System Component 6CE-12411-00-00. Overview. If you work around Yamaha outboards long enough, you learn that steady engine temperature makes a big difference in how a motor performs. The Yamaha Thermostat 6CE-12411-00-00 helps regulate coolant flow so the engine warms up properly and stays within its designed temperature range. It is a small component, but it plays an important role in keeping larger offshore motors running smoothly. Many boat owners replace the