How do you cool a marine engine?

How do you cool a marine engine?

Engine cooling systems on boats

Some boat engine malfunctions are unavoidable, but those caused by a lack of maintenance or frequent checks can be prevented. Failing to maintain an engine's cooling system is a well-known example of this, thus it is well worth spending time checking over the cooling system both ashore and afloat.

Indirect cooling

Many boat engines are cooled by a combination of fresh water and sea water, often known as raw water, via an indirect cooling system. Raw water refers to the water in which the boat is floating; in an inland river, this may be fresh water, but at sea, it will be salt water.

An indirect cooling system works as follows. Raw water enters the boat via a seacock and is filtered to eliminate weeds and trash. It then travels through hoses and a pump to a heat exchanger before exiting the boat via the exhaust system.

The fresh water is contained in an enclosed system similar to a car's cooling system, which uses a combination of fresh water and antifreeze supplied by a header tank that can be topped up as needed. The fundamental distinction between an automobile and a marine engine is that the marine engine employs a heat exchanger rather than a radiator. The fresh water flows around the engine and passes through the heat exchanger, which is normally part of the header tank on smaller engines but may be separate on bigger engines. Once in the heat exchanger, the fresh water is cooled by the raw water, which is circulated through tiny diameter cooling tubes - note that the raw water and fresh water do not mix. The sea water is then fed into the exhaust system, where it mixes with the exhaust gases and is eventually pumped out of the exhaust into the sea.

Direct cooling

Direct cooling is the most basic engine cooling system, in which raw water is pushed through the engine block and back out to sea, with no auxiliary freshwater system used. This may appear to be a simpler solution, but corrosion can be a serious problem.

When multiple names are given to parts of a boat, it can be perplexing, and the cooling system is no exception. To summarize, sea water cooling is also known as raw water cooling. If no fresh water is used, it is often referred to as a straight cooling system. If raw water is involved, fresh water cooling is also known as indirect cooling.