Maximize performance and efficiency by running your engine at the optimum temperature.A failed thermostat can cause an engine to run outside of its optimum temperature range adversely affecting performance and efficiency. The fix can be as simple as replacing the thermostat.Sierra eliminates time spent sourcing individual parts by packaging the thermostat with all the necessary components for replacement. Kits include the thermostat (144F temperature rating), gaskets and O-rings required to replace those found on GM based V6 and V8 engines newer than 1983 with standard cooling systems.For 50 years Sierra has been producing parts engineered to meet or exceed the OEM specifications and has gained the confidence of engine manufacturers and boat builders. Boaters and technicians can be assured a Sierra part will fit right the first time and restore function to OEM specifications.Key FeaturesAll thermostat kit components meets or exceeds manufacturer specificationsComplete kit includes thermostat, gaskets and O-rings to eliminate time spent sourcing individual partsThermostat has a temperature rating of 144FCompatible with 1983 and newer GM based V6 and V8 applications with standard coolingSierra Part Number 18-3668D Application TableApplicationOEM Part NumberGLM13390Mallory9-43150MerCruiser Sterndrive807252T4, 807252Q4The Sierra Engine Parts SelectorIn addition to thermostat kits, we offer a wide variety of other engine parts manufactured by Sierra. To see if we have the part you need, see ourEngine Parts Selector, where you can search by engine make, serial number and model or year of manufacture.