Maximize Yamaha outboard performance and efficiency by running at the optimum temperature 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 is engineered with a temperature rating of 122F (50C) and is compatible with many Yamaha outboards. 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. Boaters and technicians can be assured a Sierra part will fit right the first time and restore function to OEM specifications. Key Features Thermostat meets or exceeds manufacturer specifications Temperature rating of 122F (50C) Compatible with Yamaha outboard engines The Sierra Engine Parts Selector In 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.ApplicationOEM Part NumberMallory9-43035Yamaha Outboard6E5-12411-30-00, 6E5-12411-10-00, 6E5-12411-20-00