Thermostat 76.5º 119593-49550

Function and technical context

The thermostat with opening at 76.5 °C regulates the coolant temperature in the fresh water circuit of the Yanmar 6LY and 6CZ series marine engines, keeping the engine within the optimal operating thermal range. Located in the fresh water cooling pump section (position 14 of part 20), this component acts as a thermostatic valve that delays the circulation of the coolant liquid until the engine reaches its working temperature, favoring rapid and uniform heating. If the thermostat is stuck in the closed position, the engine overheats quickly; If it remains open permanently, the propeller works below temperature, increasing internal wear, fuel consumption and emissions. Since these high-power Yanmar engines operate in demanding boating applications, a bad thermostat can compromise both the performance and safety of the boat.

When to replace this part?

The most common symptoms of a faulty thermostat in Yanmar marine engines are the temperature needle that rises above the normal range or, conversely, that never reaches the operating temperature even if the engine has been running for some time; Overtemperature warnings may also appear on the instrument panel or loss of efficiency in the dashboard heating. It is recommended to check the thermostat during each seasonal maintenance and replace it every 1,000-1,500 hours of operation or if there are any symptoms of thermal irregularity. Replacing it preventively is a simple and economical measure that prevents serious damage to the cooling system when the boat is at sea.