Why should a thermostat be replaced?
It is rare that a thermostat goes bad, but it does happen. If you find that a thermostat is bad, do not think that you should discard it and operate your boat motor without it. The thermostat of an outboard motor is crucial in warming the engine to it's proper operating temperature. If an outboard engine is operated without a thermostat installed, it will suffer in some way either from poor performance or can cause internal motor damage. All outboard two stroke and four stroke motor's are designed to operate at specific engine temperatures, and if it does not obtain the correct operating temperature, it will run sluggish and cause the fuel & oil mixture to not burn properly, which causes carbon buildup. Carbon buildup causes problems with the piston rings becoming stuck in the piston ring grooves, and when this happens, it will allow the piston to touch the cylinder wall, and scoring will result. When a piston and cylinder wall start's scoring, the motor will need a complete rebuild or overhaul. Do yourself a favor and change the impeller/water pump every two or three year's regardless of usage. If you live around the ocean's, and operate your outboard motor in salt water, be sure to flush your motor with fresh water after each use.
