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What is difference between engine for ships and automobiles?
The car we normally drive, the engine is located under the hood.
The engine under the hood rotates and transfers power to the tires depending on how hard we hit the gas pedal and cars are driving at great speeds on the highway.
So what kind of engines power ships at sea?
The principle of ship’s engine may vary depending on the size of ship.
For the fun activity purpose, jet skiing (also called water bikes which may not be considered as ship) employs water jet engines.
It moves forward by sucking in water and spraying it vigorously backwards.
The engines commonly used on small ships, such as fishing boats, and medium-sized ferries are four-stroke engines.
Car engines are called “short stroke” or “long stroke” based on stroke length but they are also 4-stroke engines.
The engines for medium and large ships.
The car’s engine is four-stroke. Medium and large ships employ two-stroke engines.
The engine repeats intake→injection→explosion→exhaust.
One series of movements is two strokes when the piston rod performs in two cycles, and four strokes when it is done in four cycles.
The two-stroke is designed to intake and exhaust air at the same time. The four-stroke does the intake and exhaust one by one.
What’s the difference between two-stroke and four-stroke?
Two-strokes have more horsepower because fuel is injected and explodes on each stroke. Fuel consumption is poor.
Four-strokes are fuel-efficient and good for the environment, as they can ‘exhaust’ the exploding and burning fuel completely and ‘breathe’ clean air to ‘detonate’ the fuel.
The size is so different!
Of course, the engines must be huge, because some ships even carry cars as cargo!
Picture this: a car engine is about a man’s knees! A ship’s engine is four stories high!
They are such different in size.
Car engines need horsepower when the car starts to move, but once it starts to move, the engine will have a high revolving output to achieve speed.
Ships’ engines are built to carry large amounts of cargo and produce horsepower to keep up with the weather and currents.
The structure of the floor is designed so that the crew can always monitor the vessel, as human lives are at stake in the event of a malfunction.
Photo credits：
https://www.dieselgasturbine.com/news/Biggest-MAN-On-The-Sea/7001026.article
If you compare the size of a car to that of a ship, you would expect the engine for the ship to be bigger, but you would be surprised that it could be four stories high.
For large tankers, one might say that a city is moving at sea.
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Further reading.
