Yamaha - Thermostat Cooling System Component 6H7-12411-01-00. Overview. Thermostats are one of those parts that quietly control how your engine lives or struggles. If it sticks open or closed, you'll either run too cold or start overheating-and neither is good long-term. I've replaced plenty of these on Yamahas where the motor just wasn't holding a steady temp. Once it's working right, everything settles into that smooth, consistent operating range.. Key Features. Regulated Engine Temperature - Maintains proper operating temperature for optimal performance.. Responsive Opening Design - Adjusts water flow based on engine heat conditions.. Corrosion-Resistant Construction - Built to handle constant exposure to water and heat.. Factory-Spec Fitment - Ensures proper sealing and integration within the cooling system.. Supports Engine Efficiency - Helps improve combustion performance and reduce wear.. Engine & Boat Compatibility. Designed for Yamaha outboard engines with compatible cooling s