Maximize performance and efficiency by running your engine at the optimum temperature A failed thermostat can cause an engine to run at outside of its optimum temperature adversely affect performance and efficiency. The fix can be as simple as replacing the thermostat. Sierra makes it easy by packaging the thermostat with all the necessary components for an easy out the box installation. This thermostat has a temperature rating of 160 degree and is designed for use with many GM based engines newer than 1987 with standard cooling systems. Gaskets and O-rings are included to make the job quick and easy. For 50 years Sierra has been producing parts engineered to meet or exceed the specifications of marine engine manufacturers and has gained the confidence of engine manufacturers and boat builders to a point of supplying them with OEM parts. Boaters and technicians can be assured a Sierra part will fit right the first time and restore function to OEM specifications.