Yamaha - Thermostat Gasket 61A-12414-A0-00. Overview. The Yamaha 61A-12414-A0-00 Thermostat Gasket provides a reliable seal between the thermostat housing and engine components in Yamaha outboard motors. This gasket ensures that coolant flows correctly through the thermostat assembly while preventing water leaks that could reduce cooling system efficiency.. Thermostat gaskets are exposed to constant heat cycles, water pressure, and engine vibration, which can cause them to compress, crack, or de