The Sierra 18-3555 Thermostat is designed to regulate engine operating temperature by controlling cooling-water flow in Mercruiser applications. It replaces Mercruiser 991551.
Temperature Rating: 160°F
Fits: 1998 & newer GM V6 & V8 engines with closed cooling
Use With:
Thermostat Kit-Â 18-3667
Thermostat Kit-Â 18-3568
Need help with fitment? Contact us with your engine model and serial number and we'll help check suitability.
What is Sierra 18-3555?
Sierra 18-3555 is an aftermarket thermostat for Mercruiser applications.
Which part numbers cross-reference Sierra 18-3555?
This listing cross-references Mercruiser 991551, GLM 13040 and Mercruiser 99155A1. See the Cross References & Alternative Products section above for linked alternatives where available.
How can I check whether Sierra 18-3555 fits my Mercruiser application?
Contact us with your engine model and serial number and we'll help check suitability.
Australian Dollars
