Motorboat Expert

Independent Yachting Magazine

7 main causes of boat engine failure

Causes of boat engine failure

Updated on June 9th, 2024

The causes of breakdowns that entail unplanned shutdowns of internal combustion engines on boats and yachts do not change from year to year, so we decided to compile a small rating of malfunctions. Let’s start with the most common cause of motor failure:

1. Electrical equipment

Wiring often fails mainly due to exposure to moisture and salt. Sea water in the hold or in the engine compartment does not mix well with electricity. In gasoline engines, failures in the ignition system most often occur. In addition, many yachtsmen miss the moment when it is necessary to update the starter batteries. The electronics that control the operation of the power plant are also prone to failure.

2. Fuel system

The second most common cause of failure. Marine engines have different fuel supply systems, depending on the design and type, but in all cases, fuel filters and nozzles can become clogged.

Also, water can get into gasoline or diesel, air leaks can form in the places where the mixture is supplied, or the fuel pump can break. Among the most common cases, it is necessary to mention the most banal – lack of fuel.

3. Overheating

All marine engines have a cooling system. This may be a variant of direct seawater cooling, or indirect cooling may be used, when fresh water circulates in a closed circuit, and the radiator through which it passes, transfers the accumulated heat to the seawater, which is called “raw”.

Outboard water is supplied by a water pump. In this pump, the most critical element is the impeller, which is most often made of soft materials. It is he who regularly breaks down.

Another culprit for overheating is debris floating in the sea. It tends to clog the water pump intakes. In this case, the impeller may burn (melt). Also (quite rarely) the thermostat valve sticks in the closed position.

Fortunately, modern engines are protected from overheating and have a variety of warning and emergency shutdown systems. However, older models of yacht diesels and gasoline ICEs may be vulnerable to such problems.

4. Propeller

A propeller can be broken by hitting an underwater obstacle or during grounding. But most often he collects various garbage under water. Fishing nets and other rubbish that people throw into the ocean winds up very well on the propeller. The consequences depend on the design of the drive. Sometimes a thin fishing line, wound around a shaft, can ruin seals.

5. Reducers

Unlike direct drives, angular torque transmission is a more complex mechanism in which the gears of the gearbox are constantly meshed under load, so their failure is quite likely. Water entering the gearbox seriously increases this likelihood.

6. Drive belts

Yes, they wear out, stretch and even tear. Therefore, it is a good idea to have a spare set of belts on board.

7. Mechanical failures

In a yacht engine, consisting of hundreds of parts under continuous load, anything can break down at any time. Piston rings, camshafts, timing valves and even cylinder heads. In this case, only towing will save the motor boat.