Yamaha - Thermostat Cover Cooling System Housing 6E9-12413-00-1S. Overview. Thermostat covers don't seem like much until you've got a leak or temperature issue to track down. I've seen engines run hotter than they should just because this cover wasn't sealing right. It holds everything together around the thermostat and keeps water flowing where it needs to go. When it's in good shape, the cooling system stays consistent and you don't have to think twice about it.. Key Features. • Secure Thermostat Housing - Keeps the thermostat properly positioned for consistent cooling performance.• Leak Prevention Design - Helps maintain a tight seal to prevent water loss.• Durable Construction - Built to handle engine heat and continuous water exposure.• Proper Water Flow Routing - Supports efficient circulation through the cooling system.• Exact Yamaha Fitment - Matches factory specifications for proper alignment and installation.. Engine & Boat Compatibility. Designed for Yamaha outboard engines