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Do Outboard Motors Have Air Filters?

Do Outboard Motors Have Air Filters?

If you’ve spent any time looking at the engines of your car, lawnmower, or chainsaw, you probably saw that an air filter was one of the components. 

On the other hand, if you’ve ever looked at your outboard motor, you may have been surprised that you couldn’t find any air filter. After all, don’t all small engines have air filters built in?

Not always.

Some small motors simply don’t need this air filter because of the conditions they operate under. So, what about outboard motors? Do some of them have air filters, or do they not need them?

Keep reading as we dive into this topic.

What Are Air Filters For?

First off, we should discuss why some engines have air filters.

As you might expect, the purpose of an air filter is to clean the air going into an engine. Dirt, grime, and other things being sucked in with the air can clog the engine, mix with and ruin fuel, etc. 

Impact of a Dirty Air Filter on a Modern Engine

An air filter removes as many of these things as possible, purifying the air that passes to the inner parts of the engine.

Cleaner air results in less outside material getting into the engine, where it can cause build-up, corrosion, and wear. So, engines with air filters should, theoretically, last longer than those without them.

Air filters are frequently installed on engines that operate in poor conditions. For example, car engines are exposed to lots of dust, dirt, leaves, grass clippings, insects, and other random bits of debris. 

Air filters are not used as much on engines that operate in purer, cleaner air or a more controlled environment. Again, air filters are designed to clean the air, and this isn’t always necessary.

Do Outboard Motors Have Air Filters?

air filter in outboard motors

Most outboard motors don’t have air filters. Some may have air silencers or air boxes that filter out some things, but these aren’t actually filters. Outboard motors with real air filters are hard to come by.

The reason is that outboard motors generally don’t need air filters; the air over water is much cleaner than the air over land, so the engine is operating under much better conditions than, say, a car or lawnmower engine. 

What’s more, most outboard motors simply don’t log as many hours of use.

For comparison, car engines are generally used for hundreds of thousands of hours in dusty, dirty conditions. 

Boat engines may be used for a few thousand hours, at best, and they are always used in cleaner, clearer air.

In fact, even without an air filter, your engine probably won’t die because of dirty air. It’s more likely your outboard motor will die from wear and tear to other components. 

All that most of these engines suck in over a lifetime are a few insects, and these generally won’t cause any issues with the engine.

Another important consideration is the humidity levels in marine environments. The moisture over lakes, rivers, and oceans can clog air filters, which in turn could lead to problems with the fuel/air mix required for combustion. 

In other words, air filters on outboard motors could potentially cause starting problems.

That said, some people feel an air filter is necessary for their specific boating conditions. 

They may invest in an outboard motor with an air filter, such as those produced by Mercury, or they may add an air filter to their existing outboard.

When to Add an Air Filter?

when to add an air filter

You may be wondering, when would it be a good idea to have an air filter on your outboard? Let’s take a look at some example scenarios.

  • Urban areas: If you do a lot of boating on small bodies of water in urban areas, the air around the water is probably not as clear as it would be in a more rural location.
    The air may not seem particularly dirty to you, but it could be bad for your engine if you’re logging lots of hours in this kind of environment.
  • Smoggy areas: The air quality may be particularly poor over rivers or lakes in large cities or industrial areas. For example, the air around Los Angeles is frequently thick with smog.
    If you spend a lot of time boating in smoggy locations, you may want to use an outboard motor with an air filter. 
  • Coastal areas: Beaches, especially those with shallow waters and lots of sandbars, may have a fair amount of sand and dust in the air.
    If you are further away from the shore, it may not be as much of a problem; but if you stay close to shore, you may want to have an air filter on your outboard.

How to Install an Air Filter?

Air Filter Fit for Mercury 4 Stroke Outboards Engine Replace

Click the image for more info

This leads to the question: how do you install a filter on your outboard motor? 

The answer may depend on whether your engine already has a filter that simply needs to be replaced, or if you’re adding a filter onto a motor that doesn’t have one.

If your motor already has an air filter and it needs to be replaced, take it to a marine repair shop or follow the instructions in your owner’s manual to replace the filter yourself. 

Check out this video for an example of how to change an air filter on an outboard motor: 

How to replace Defective Mercury Outboard Air Filter on EFI Four Stroke75hp 90hp 115hp

If you’re looking to add an air filter to an outboard that doesn’t already have one, your best bet is to make one yourself. 

You can check out how to make a simple air filter for small engines by watching this video: 

Make your own air filters

To install the DIY filter on your outboard motor, place it over the air box on your carburetor or on the air intake valve on the cowling. 

Secure it in place using screws, super glue, or bungee cords, being careful not to damage any components of the motor.

Though this isn’t the most professional option, it will get the job done.

Which Engines Need Air Filters?

engines need air filters

We’ve established that not all outboard motors need air filters because they operate in relatively clean, clear environments. 

On the other hand, some types of engines wouldn’t last long without an air filter. Some of these engines include:

  • Car, truck, motorcycle: All of these vehicle types need air filters because their engines have to last for many years and are constantly sucking in dirty air. The filters purify the air as much as possible, extending the life of the engine by keeping it clean.
  • Lawnmower: Lawnmowers are constantly kicking up dust, dirt, and grass clippings among other debris that might be in the yard. Without air filters, these engines would soon become choked out with all this debris.
  • Weed whacker: Like lawnmowers, weed whackers toss up all kinds of dust and yard debris. Air filters are necessary to clean all of this stuff out of the air before it is pulled into the engine.
  • Chainsaw: Chainsaws create sawdust, which fills the air around a work site and can easily be sucked back into the engine. For this reason, many chainsaws have air filters to keep the motors from becoming clogged.

Conclusion

Most outboard motors do not have air filters. This is because the air over water is usually pretty clean, so air filters are not necessary to clean the air before it is pulled into the engine.

The main purpose of an air filter is to clean the air, so they are often included in motors of cars, lawnmowers, chainsaws, and more. Some people prefer to have them on their outboard motors, though they often have to make their own filters.

If you choose to install a filter on your outboard motor, be aware that it could lead to issues with starting the engine. Good luck and stay safe out there!