A conventional marine diesel engine produces power when hot compressed air ignites fuel sprayed under very high pressure into the cylinder head. A marine diesel engine does not require a carburetor to mix fuel and air or spark plugs to ignite the mixture. Instead it employs the pistons to compress the air to 3000 kPa which causes it 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 plugs in the inlet manifold or a glow plugs in the pre-combustion chamber of each cylinder to provide additional heat to the combustion air during starting.
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.
Every boat owner should have an understanding of the regular marine diesel engine maintenance chores like changing the engine oil, replacing the water pump and checking fuel filters and lines.
An excellent guide for beginners is Laurence Burgin’s “Marine Diesel Engines for Beginners”. This handy downloadable e-book can be printed out, inserted in plastic sleeves and taken into the engine room with you when you are looking after your engine. It is well illustrated and contains easy-to-follow and well-written instructions on many aspects of marine diesel maintenance including:
- Oil systems
- Changing the engine oil
- Exhaust systems
- Tools you must carry for both inshore and offshore
- Engine cooling systems
- Electrical theory and systems
- … and much more
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