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Jun 5, 2023  •  6 min

Air Cooled Outboard Motor: How Does It Work

Are outboard motors air cooled? How does an air cooled outboard motor work? Is the air-cooled engine good? Air cooled or water cooled outboard motors, which is better?

While searching for your ideal outboard motor, you might hear people talking about air cooled vs water cooled ones and be confused about their differences (especially if you are new to the outboard world).

Here we will have all the essentials concerning air-cooled outboards explained in one article.

Spend a few minutes with us, and you will know if the air-cooled outboard motor is a good fit for you.

Table of content:

Air Cooled Outboard Motor Applications

What Is Air Cooled Outboard Motor

Air cooled outboard motors are a type of outboard that rely on air circulation directly to eliminate engine heat. They typically use a system of cooling fins and deflector plates.

Simply put, the air cooled outboard is cooled as air passes over. In comparison, the water cooled outboard uses (raw/natural or fresh) water to absorb heat from the engine.

As you can imagine, air cooling systems don’t require as much power and are not as effective as water-cooled systems. Therefore, the air cooled outboard motors are better suited for small horse-powered outboard engines.

Although ideal for some particular boating situations where getting enough fresh water is a problem, such as skinny water boats or mud outboards, the air-cooled types are not as popular in marine applications.

Editor’s Note: If you prefer an air-cooled outboard motor just for the fear of saltwater/weed intake or the outboard coming out of water in waves which affects the cooling system, a natural cooling system would be a better solution.

How Does Air Cooled Outboard Motor Work

Outboard motor cooling systems work similarly to your cars or motorcycles. As mentioned, the air cooled outboards use a fan to draw air over the hot areas (the engine and exhaust manifold) to dissipate engine heat.

In comparison, with water-cooled outboards, the lake or sea water is pumped through the engine block and then ejected to achieve the cooling effect.

Some modern water cooled outboards, such as ePropulsion, adopt natural cooling for motors, which avoids cooling water intake and circulation. Therefore, no worries about fresh water availability or getting stopped with the intake of weeds like milfoil, hydrilla and the like.

ePropulsion Outboard Motors with Natural Cooling

Due to the traditional air-cooling working mechanism, the outboard is less efficient in dealing with the constantly changing temperatures. It requires either larger surface or ambient air and movement (like motorcycles and aircraft) to spread the heat out more quickly.

That’s why you can only find a few small air cooled outboard motors on the market. If you are looking for bigger outboards (larger than 5 hp), you will be very likely to get a water cooled one.

Continue reading to quickly learn the differences between air cooled vs water cooled outboards and the pros and cons of each.

Air Cooled vs Water Cooled Outboard

There are two types of cooling systems, namely air cooling and water cooling, and the most common type is the water cooling system.

So why is that? What’s their difference? How does it affect outboard performance?

The major differences between air cooled outboards and water cooled ones are their working mechanisms (as explained above) and maintenance steps.

The difference in how outboard motors work can result in great differences in your boating experience.

It’s easily understood that air and fan movement makes noise itself, which can be loud and annoying during your boating trips. In contrast, the water cooled outboards are quieter since they are surrounded by a jacket of water, which helps deaden the sounds.

In terms of maintenance, the air-cooled outboard requires you to remove dirt from between the cooling fins regularly. You need to avoid the dirt that sticks to the oily residues on the outboard, which can act as insulation and affect the cooling effect.

By contrast, the water-cooled outboard requires you to replace pump impellers (usually every 2 years). This can help avoid clogged pumps and corrosion, which is a major cause of outboard overheating problems.

You are also expected to clean the water filters regularly (in every few dozen hours) to keep the water-cooling system in good condition.

Which Is Better: Air-cooled or Water-Cooled Outboard Motor?

Wondering whether the air cooled outboard motors or the water cooled ones is a better suit for you?

Here I’ve summarized the pros and cons of each to help you easily decide whether to go with air-cooled outboards or the other way.

Air Cooled Outboard Motor:


  • Easier maintenance with easy notice to the cooling fan problems
  • Less worries about broken impeller, blocked intake, salt in water passages etc
  • No worries about mud intake in super skinny waters


  • Loud noise due to the lack of water surrounding the cylinder
  • More prone to overheating problems

Water Cooled Outboard Motor:


  • Higher efficiency in dissipating engine heat and dealing with temp extremes
  • Tighter tolerances, smoother operation, and prolonged component life
  • Easier to run at a specific temperature with water cooling
  • Quieter with water cutting down on noise levels significantly


  • Requires more maintenance work

Can I start an air-cooled boat motor out of water for a test?

The short answer is yes, as long as the outboard motor is totally air cooled without impellers and in a very short period of time. Anyways, it’s recommended to follow the outboard handbook and instructions from the manual.


Generally speaking, the air cooled outboard motor is easier to maintain but with more noise and overheating problems.

In fact, these days, the vast majority of outboards are cooled by the water the boat is used in, and air cooled outboards are favored in some specialized applications. If you are a duck or goose hunter and looking for a mud motor, the air cooled outboard motor is a great solution.

If you are still not sure about whether to go with an air-cooled outboard or a regular water-cooled one, leave your comment below or talk to our specialist directly for professional advice.

Join the discussion!

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