The Marine Engine Explained
A marine engine is the propulsion system used to power boats and ships. It is a specialised internal combustion engine built to withstand the elements and the harsh saltwater environment.
The marine engine is a hefty piece of machinery. The largest 2-stroke marine engine is capable of producing up to 80,010 kW of power—enough to power 110,000 Toyota Corollas at full speed. And it is critical to world trade. Around 80% of the world’s trade by volume is transported by marine engines.
Marine engines are designed slightly differently from other engines. They don’t need quick, variable speed changes like a car engine would—constant, safe, reliable, and efficient power is more important at sea.
However, they are generally powered by an internal combustion engine, similar to cars. The main difference between marine and automobile engines relates to the power they must generate and the environment they operate in. Whereas a car only has wind resistance to power through, ships and boats must plough through strong waters. And while cars don’t suffer particularly from the environment, marine vessels must be built to resist the salty environment which can cause corrosion to metal components.
Let’s examine the inner workings of a marine engine and find out why cast iron is often used to manufacture marine components.
Marine Diesel Engine Components
As you can see, a marine engine can be quite a sizeable piece of machinery. There are 11 main components that make up a marine diesel engine:
| BEDPLATE | The foundation block of the engine onto which the other engine components sit. | CAST IRON |
| A FRAME | Sits on top of the Bed Plate and supports the cylinder block. | CAST IRON |
| CRANKSHAFT | A critical component that sends power along the piston rods to the propeller shaft. | STEEL |
| CAMSHAFT | Controls the inlet, exhaust and fuel injector valves | CAST IRON OR STEEL |
| PISTON | Converts the force of combustion energy from the crankshaft to the propellor. | CAST IRON |
| PISTON RINGS | Seals the combustion chamber. | CAST IRON |
| CYLINDER BLOCK | Rests on top of the A-Frame to house other parts of the engine. | |
| CYLINDER LINER | Heat resistant to prevent heat from escaping the combustion chamber. | CAST IRON |
| CONNECTING ROD | Transfers power from the piston to the crankshaft | STEEL |
| Supporting structure for the valves and allows correct deployment of cooling water, air and fuel. | CAST IRON | |
| INLET AND EXHAUST VALVE | Allows air into and out of the combustion chamber. | CAST IRON OR STEEL |
| TURBOCHARGER | Increases the power and efficiency of the engine. | CAST STEEL |
Why Use Cast Iron For Marine Components?
Cast iron has been the trusted choice for marine engine component manufacture for many years, and it offers huge benefits:
- Wear Resistance – cast iron has great corrosive resistance, and this is particularly beneficial in the harsh saltwater environment.
- Castability – cast iron is relatively easy to forge and machine into complex components that often make up a ships drawings.
- Cost – cast iron is cheaper than its alternatives, which is clearly important for large-scale projects.
- Compressive Strength – cast iron is robust and capable of high impact stress resistance.
- Temperature – cast iron is able to withstand extremely high temperatures.
- Durability – cast iron has a reputation for dependable performance over long periods of time.
Marine engine components are not the only marine application where cast iron is the material of choice for manufacture. It is also commonly used to produce rotating equipment, pumps and generators.
However, the immense durability of cast iron can sometimes require repair. Over time, the microscopic cracks inherent within the material can develop into more serious cracks. Cast Iron Welding Services has developed a tried-and-tested process to repair cracks in cast iron. We will ensure your marine component is safely back in working order and save you the cost of buying new. Sustainability is important, and by restoring and repairing, we can reduce waste and preserve resources to benefit the environment.
Marie Palmer
Director
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