Yamaha - Thermostat Seal Cooling System Sealing 6EK-12412-00-00. Overview. Seals like this might be small, but they can cause big problems if they're not doing their job. I've seen engines run hot or leak just because a thermostat seal was worn out or reused one too many times. It sits right where water flow needs to stay controlled and contained. When it's fresh and seated properly, the cooling system stays tight and reliable.. Key Features. • Reliable Cooling System Seal - Keeps water contained within the thermostat housing for proper flow.• Leak Prevention Design - Helps eliminate water leaks that can affect engine temperature control.• Heat-Resistant Material - Built to handle engine heat and continuous cooling cycles.• Proper Fit Sealing Surface - Designed to align correctly with thermostat housing components.• Direct Yamaha Replacement - Matches factory specifications for dependable installation and performance.. Engine & Boat Compatibility. Designed for Yamaha outboard engines u