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How Do Marine Engines Work?

You love fishing, diving, and sailing out on the open water. That’s why you decided to join the more than 25 million Americans who own a recreational boat.

As much as you love your boat, you’re not sure how the engine works. Does it function as a car engine does? What are the differences?

We put together a quick guide to explain how marine engines work and how they differ from car engines. Keep reading to learn more about how your boat engine works before your next high seas adventure.

Types of Marine Engines

Like cars, boats can have a couple of different kinds of engines. These are the two most common marine motors you’ll see:

4 Stroke Engine

In the 4 stroke model of boat motors, it takes 4 steps to transfer power from the combustion chamber of the engine to the crankshaft that leads away from it. This gives the boat the ability to move and have electrical power out on the water. The 4 cycles are:

  1. Suction stroke
  2. Compression stroke
  3. Power stroke
  4. Exhaust stroke

The 4 stroke engine is less common in watercraft than the 2 stroke engines.

2 Stroke Engine

This kind of vessel propulsion motor is bigger than a 4 stroke engine. In the 2 stroke engine, the complete sequence is two cycles.

  1. suction/compression stroke
  2. Power/ exhaust stroke

The combination of functions in each stroke makes this kind of engine more efficient. That’s why larger engines tend to use a 2 stroke version.

Components of a Watercraft Engine

Manufacturers make engines in different layouts and with different arrangements of components. These are some of the common components you’ll see in ship engines.


This piece looks like the letter “A” and sits above the bedplate. It carries the crosshead guide and supports the base of the entablature.


The bedplate section is the bottom section of the engine and houses the crankshaft bearings and the A-frame. Some smaller bedplates are iron but larger ones are only steel construction.


Connecting the crankshaft in the main engine to the connecting rod that leads to the propeller is the marine bearings. These are special bearings meant to function underwater under high stress, unlike car bearings.


The lower part of the entablature (or cylinder block) attaches to the A-frame. This accommodates the engine’s cooling water and provides open airspace.

Money Can’t Buy Happiness, But It Can Buy a Boat

We live fast-paced lifestyles that can burn you out in an instant. It’s important to find hobbies like boating that help you relax and escape that grind every now and then.

Some boaters love their watercraft so much that they learn as much about the boat mechanics as possible. They want to know their vessel inside and out.

we hope you enjoyed reading this article and that you learned how marine engines work. If you’re looking for more informative articles about boats, cars, technology, and more, check out the rest of our blog today!

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