Yamaha - Thermostat Cover Cooling System Component 6DA-12413-A0-9S. Overview. This thermostat cover is one of those simple pieces that plays a big role in keeping your cooling system sealed and working the way it should. It holds everything in place around the thermostat and keeps water flowing where it needs to go. When these covers start to warp or corrode, you'll usually see it in leaks or inconsistent engine temps. Swap it out, and you're back to steady cooling and peace of mind on the water.. Key Features. Secure Thermostat Housing - Keeps the thermostat properly seated for consistent engine temperature control.. Leak Prevention Design - Helps maintain a tight seal to prevent water or coolant loss.. OEM Fitment - Built to Yamaha specifications for proper alignment and easy installation.. Corrosion-Resistant Build - Designed to handle harsh marine environments over time.. Engine & Boat Compatibility. Designed for Yamaha outboards using thermostat-regulated cooling systems. Commonly