19315-ZW5-000 Thermostat Cover - Overview. The 19315-ZW5-000 Thermostat Cover is an essential component within Honda marine engine cooling systems. This thermostat cover securely encloses and protects the thermostat, a vital part that regulates engine temperature by controlling coolant flow. By maintaining proper sealing and facilitating efficient cooling system function, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Designed