Monsoons in India…and every boat owner has packed off his or her boat to the finest boat-yard or dry-dock worth of the boat (or the owner)…

While in the yards…thorough maintenance work that cannot be done when the boat is on water…then covering it up to the extent that it is almost water-tight!

Monsoons are also the best time to expose that engine of yours…do extensive work on it with all the winding and grinding it went through in fairweather.

Diesel engines are popular since they are powerful and torquey, and have a clear advantage over gas (petrol) engines.

MARINE DIESEL ENGINES

Power in a conventional marine diesel engine is produced by hot compressed air igniting fuel sprayed under very high pressure into the cylinder head.

Gas-powered engines use a carburetor to mix fuel and air or spark plugs to ignite the mixture. That is not the case in diesel engines and instead they employ the pistons to compress the air to 3000 kPa.

This causes the mixture to become extremely hot and the fuel is ignited as soon as it is injected into the cylinder.

Some marine diesel engines are fitted with a heater plug in the inlet manifold or a glow plug in the pre-combustion chamber of each cylinder to provide additional heat to the combustion air during starting.

WHY DIESEL ENGINES?

Diesel engines are heavier and slower revving than petrol engines but they are also more reliable because they do not rely on external carburetion or an electrical spark for ignition.

Newer engines use an electronic fuel injection system whereby fuel and air are mixed more thoroughly in the pre-combustion chamber before entering the cylinder. This system maximizes power and fuel economy and is also less polluting.

FOUR STROKE DIESEL ENGINES

The four strokes in the order they occur are:-

1) Inlet stroke – With the inlet valve open and the exhaust valve closed, the piston moves from top to bottom, creating a low-pressure area in the cylinder. Clean, filtered air rushes through the open inlet valve to relieve this low-pressure area, and the cylinder fills with air.

2) Compression stroke – With both valves closed, the piston moves from bottom to top, compressing the air. During this stroke the air becomes heated to a temperature sufficiently high to ignite the fuel.

3) Power stroke – The fuel is injected, or sprayed, into the hot, compressed air, where it ignites, burns and expands. Both valves remain closed, and the pressure acts on the piston crown, forcing it down the cylinder from top to bottom.

4) Exhaust stroke – The exhaust valve opens and the piston starts to move from bottom to top, driving the burnt gas out of the cylinder through the open exhaust valve.

TWO STROKE DIESEL ENGINES

The two-stroke engine uses two piston strokes to complete one power stroke and, therefore, fire twice as often as a four-stroke engine.

A two-stroke engine is smaller and simpler with fewer moving parts. A two-stroke engine has the potential to produce twice as much power as a four-stroke engine of the same size, however, because of the extra fitting required in a two-stroke diesel engine, for example blowers and governors, they become more expensive to produce.

There has been a shift towards four stroke diesel engines which have become more efficient and smaller.

PROTECTING YOUR DIESEL ENGINE

1) All boat owners should have an understanding of basic marine diesel engine maintenance to keep themselves and their families safe on the water.

2) Regular maintenance and checks of the engine are mandatory.

3) Use optimum quality fuels and oils; this would not only benefit your engine but also the environment.

4) Avoiding long periods (more than 10 minutes) of idling in a “no-load” situation. Many owners who don’t regularly use their boats often put ‘on’ their engines and run them idle. This infact glazes the bores of the engine and cause premature engine failure. If the vessel is in a berth the engine can be put in gear to create load at idle.

Giira Yachts hopes to benefit every boat owner in every manner. Do email your queries with regards to boat maintenance to give you assured maintenance advice.

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