The thermostat in your 2012 Evinrude E-TEC 90HP outboard engine plays a critical role in managing the engine’s temperature by regulating the coolant flow. If it fails, your engine might overheat or run too cold, leading to various issues.

Removal:

1. Thermostat Cover

To remove the thermostat, begin by taking off the thermostat cover and the O-ring from the cylinder head. Be careful to avoid causing any damage to the components. Then, proceed to remove the spring, thermostat, and gasket. If you need to replace the cylinder head thermostat seal, you’ll have to take off the cylinder head. When installing a new seal, ensure that the side marked “TO CYLINDER HEAD” faces the thermostat.

Inspection:

Examine all parts meticulously for any signs of cracks, heat damage, or corrosion. Replace any parts that are damaged. Make sure to clean any debris from the housing and parts to keep everything functioning properly.

Installation:

Reassemble everything in the reverse order of disassembly. Apply a gasket sealing compound to the threads of the thermostat cover, and install a new O-ring. Tighten the thermostat cover to a torque of 120 to 144 in. lbs. (13.5 to 16 N·m).

1. Cylinder Head Seal

Changing the thermostat on your Evinrude E-TEC 90HP involves careful removal and inspection of parts, replacing any that are damaged, and reassembling with attention to detail. Following these steps will help ensure your engine runs efficiently and avoids overheating issues.

Good luck with your repair! If you have any more questions, feel free to ask.