The Sierra 18-3638 Thermostat replaces Mercury 804540 for Mercury Outboard applications. It regulates cooling-water flow as the engine warms and cools, helping maintain the intended operating temperature.
Fits:Â Mercury 2.5-3.5HP (0R131842 & Up), 4-6HP (0R411838 & Up)
Need help with fitment? Contact us with your engine model and serial number and we'll help check suitability.
What is Sierra 18-3638?
Sierra 18-3638 is an aftermarket thermostat for Mercury Outboard applications.
Which part numbers cross-reference Sierra 18-3638?
This listing cross-references Mercury 804540. See the Cross References & Alternative Products section above for linked alternatives where available.
How can I check whether Sierra 18-3638 fits my Mercury Outboard application?
Contact us with your engine model and serial number and we'll help check suitability.
Australian Dollars
