Optimum engine temperature maximizes performance and efficiency. A failed thermostat can cause an engine to run at outside of its optimum temperature and can adversely affect performance and efficiency. The fix can be as simple as replacing the thermostat. This Sierra thermostat has a temperature rating of 120 and is compatible with many Mercury and Sear outboards. Sierra thermostats are engineered to meet or exceed Mercury and Sear specifications to give boaters and technicians confidence of an OEM fit and function. Key Features Thermostat meets or exceeds manufacturer specifications Temperature rating of 120 Compatible with many Mercury and Sears outboards; use the list below or our Engine Part Selector to confirm this thermostat is right for your engine 18-3549 Application GuideApplicationOEM Part NumberGLM13120Mallory9-43014Mercury Marine14586Sears14586The Sierra Engine Parts SelectorIn addition to thermostats, 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.