Yamaha - Thermostat Cover Cooling System Component 6L5-12413-00-1S. Overview. The thermostat cover isn't something you think about often, but when it starts leaking or warping, it can mess with your cooling system fast. I've seen small leaks here turn into bigger overheating issues if they're ignored. This is one of those simple parts that keeps everything sealed and functioning the way it should. Swap it out when needed, and you avoid a lot of unnecessary trouble down the line.. Key Features. Secure Thermostat Housing Seal - Keeps the thermostat properly enclosed to maintain cooling system pressure.. Corrosion-Resistant Construction - Built to handle constant exposure to water and marine conditions.. Factory-Spec Fitment - Designed to match Yamaha components for proper alignment and sealing.. Leak Prevention Design - Helps eliminate coolant leaks that can affect engine temperature.. Essential Maintenance Component - Ideal for replacing worn or damaged covers during service.. Engine &