Yamaha - Thermostat Seal Cooling System Sealing Component 6FM-12412-00-00. Overview. The Yamaha Thermostat Seal 6FM-12412-00-00 is one of those small parts that can cause big problems if it's not doing its job. When this seal starts to wear out or flatten, you can end up with leaks or inconsistent engine temperatures. It keeps the thermostat housing sealed so coolant flows where it's supposed to. If you're servicing the cooling system, this is one of those parts you replace without thinking twice.. Key Features. • Secure Cooling System Seal - Keeps the thermostat housing sealed to prevent leaks and maintain proper flow.. • OEM Fit Precision - Designed to match Yamaha specifications for proper seating and sealing.. • Temperature Control Support - Helps ensure consistent engine temperature by maintaining system integrity.. • Heat-Resistant Material - Built to handle high temperatures and continuous cooling cycles.. Compatibility. Compatible with select Yamaha outboard engines using this