Keeping the engine at the correct temperature
The thermostat controls the flow of coolant as the engine warms up. When the engine is cold, it stays closed so the correct operating temperature is reached more quickly. As the coolant heats up, the thermostat opens and allows it to circulate through the cooling system.
A thermostat that stays closed can cause overheating. If it remains open, the engine may run too cold or take a long time to warm up. Temperature problems can also be caused by a worn impeller, restricted water flow, a faulty circulation pump or a blocked heat exchanger, so it is worth checking the rest of the
cooling system as well.
Check the opening temperature and part number
Thermostats that look almost identical can have different opening temperatures or dimensions. Do not select one based only on its appearance or diameter.
Check the original part number and the complete engine model before ordering. The cooling arrangement is also important. Directly cooled and freshwater-cooled versions of a similar engine may use different thermostats.
Some engines use more than one thermostat. The product description will state the quantity supplied and the known applications. It will also show whether a gasket, O-ring or sealing ring is included. If the seal is not included, it should normally be ordered separately.
Check the cause of temperature problems
Replacing the thermostat is sensible when it is corroded, stuck or no longer opens at the specified temperature. However, a new thermostat will not fix every cooling problem.
If the engine overheats under load, check the seawater intake, strainer, impeller, hoses and exhaust elbow. If coolant circulation is poor, inspect the
water pumps and heat exchanger. Low or contaminated
coolant can also cause problems.
When refilling the system, use the correct coolant and remove trapped air according to the manufacturer’s procedure.
If you are unsure which thermostat you need, send us the engine model, serial number and the number stamped on the old thermostat. A clear photo and the stated opening temperature can also help us identify it.
