Prevent Overheating in Boat Engines

A boat engine.

Boat engines are prone to overheating. This can cause serious damage to your boat and boat's engine if left untreated. In order to fix overheating problems you first need to do some detective work. Find out exactly what is causing the overheating problem with the boat engine and you should be able to correct the overheating problem before it has a chance to seriously damage your boat.

Causes of Overheating

Overheating is a common problem with boats and this is because of how they are cooled. Most engines are cooled by using seawater instead of using air intakes. This is beneficial because there is no risk of the engine suffocating if water gets into the air intake. However, if any of these sea intakes get blocked then it can result in the engine overheating.

Intake Pump

Take a look at the intake pump on your engine to try and find out whether or not it is blocked. It's actually very easy for these intakes to get blocked as a result of seaweed or debris floating in the sea. The intake pump will be in a different place depending on the type of engine you are using. The alpha drive engines have a pump which is located in the drive itself. Inboard engines often have a separate intake pump which needs to be inspected.

Also check that the intake pump is working properly, it could also be that this is faulty or damaged and needs some extra attention. Replacing a water intake pump is a very easy project but you will need to ensure that you purchase the right model and type of pump to work properly with your engine.

If you ever experience overheating with a boat engine then the most likely suspect is the intake pumps. A carrier bag can cause an engine to overheat for no apparent reason. If you stop to check it out then the bag often comes out and disappears making it look like a mysteriously intermittent problem. Sometimes corrosion can also cause the intake pipes to become restricted, this will cause the same problems.

If the intake pump is blocked then the engine will not be cooled properly which will mean that it will overheat.

Rubber Impellers

Inside the intake pump there is a rubber impeller. It is this impellers job to draw water into the engine. If the water iintake port was blocked then it will quite often deform this impeller, over time as the impellers get older they can also become deformed. This can reduce the amount of water which is drawn into your boat meaning that the engine can overheat.


If the exhaust manifolds are restricted then this will prevent water from flowing properly through the engine which will have the same effect as a blocked water intake.


If your engine overheats then it can cause damage to the thermostat which can cause the problem again. If the thermostat is damaged then it will cause the engine to overheat but there will still be lots of water flowing out.