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How Does a Jet Ski Air Intake Work? [Explained]

How Does a Jet Ski Air Intake Work? [Explained]

Fresh air comes into a jet ski through air passages on the top deck and below the seat. The jet ski’s OEM air intake systems feature air intake hoses and a plastic airbox. While some airboxes house an air filter, others only feature a metal flame arrestor to block backfiring from reaching the engine compartment.

If you want to learn more about how the air intake works on a jet ski, you’ve come to the right place.

We at JetDrift have compiled all you need to know under one roof!

Where Does a Jet Ski Get Air From?

Internal combustion engines need air to operate, and jet ski engines are no exception. However, jet ski engines sit inside an enclosed engine compartment.

This is why many people ask: Where does a jet ski get air from?

Simply put, fresh air enters the jet ski’s hull through air passages mounted under the front portion of the seat. However, other models feature intake grills on the top deck or front hood, or even around the neck of the handlebar.

These air intake grills were much more recognizable on some vintage skis, but on the latest models they are integrated into the design.

Fresh air comes into the jet ski through these grills and passages while hot air makes its escape through air vents under the passenger seat.

Where is the Air Intake on a Jet Ski?

The air intake on jet ski engines can be found inside the engine compartment. These simple air inlet systems typically feature four major elements, including:

  1. Airbox
  2. Air filter (on certain models)
  3. Flame arrestor
  4. Intake hoses
Let’s drill into the details and talk about these units in detail!

1. What is an Airbox on a Jet Ski?

The airbox on a jet ski is a large plastic chamber that is part of the intake system. A PWC airbox has three main purposes, which are as follows:

  • To prevent water ingestion
  • To work as an air silencer
  • To house the fuel filter or flame arrestor
It’s safe to say that one of the main purposes of a jet ski’s airbox is to keep water away from the engine.

This plastic box is intended to collect air from the engine compartment and feed it into the engine through intake hoses.

This box is mounted on the upper part of the engine compartment or on top of the engine, a safe distance from the bilge water. Even if water starts to accumulate inside the engine bay, it’s unable to reach the airbox (unless the jet ski is almost completely sunk).

What’s more, the interior design of the airbox is also engineered to stop water from getting into the engine. An oil breather vent is attached to this unit on certain models.

The airbox also works as an air intake silencer. Jet ski engines are known for their high noise emissions, which can be slightly reduced with this unit.

In most stock jet skis, the airbox intakes air from the engine compartment, but on some models, it’s attached directly to the air inlets via fresh intake hoses.

The latter design provides continuous fresh air for the engine, as the engine heats the air inside the engine compartment.

On stock jet skis, the airbox typically houses a flame arrestor and sometimes an air filter as well.

How do you remove a jet ski airbox?

If you want to remove the jet ski airbox you have to remove the intake hoses as the first step. These hoses are typically fastened with regular metal clamps. Next, you have to remove the bolts or straps that hold the box in place. Sometimes you have to take off the top of the box to access these units.

Depending on the make and the model year, the process of removing a jet ski airbox varies widely.

It’s typically much easier on vintage 2-stroke skis where there is plenty of room around the engine.

In contrast, space is limited on modern 4-stroke skis and the airbox is often mounted in a hard-to-reach place. You will probably have to pull the battery or other parts out on these machines to make more room.

Here’s a great video on how to remove the airbox on a jet ski:

Let’s move on and discuss the air filter and flame arrestor in detail!

2. Do Jet Skis Have Air Filters?

While some jet skis feature air filters, others are only equipped with a flame arrestor. The air filter is not an essential part of a jet ski as it runs on the water where there is not a lot of dust or dirt in the air.

Despite this, modern Kawasaki Jet Skis and Yamaha WaveRunners come with air filters as standard, while the competitor Sea-Doos lack this feature.

Jet ski air filters are similar to motorcycle and ATV air filters but designed for the marine environment.

Where’s the air filter installed on a jet ski?

To keep it dry and protected, the air filter on a stock jet ski is nestled in the airbox. Heavily modified and racing jet skis are often equipped with an aftermarket PWC air intake system with a performance air filter. The latter is typically mounted directly on the intake hose for better airflow.

How do you Change the Air Filter on a Jet Ski? 

To replace the air filter on a jet ski, you must remove and disassemble the airbox. The air filter is housed in this plastic box, which is usually fastened with a few simple screws. Remove these screws, replace the filter, and reassemble the airbox.

If you want to drill into the details, here’s a great tutorial on how to replace the air filter on a jet ski:

Keep in mind that most jet skis don’t feature an air filter, only a metal flame arrestor, which doesn’t require periodic replacement.

3. What is the Flame Arrestor on a Jet Ski?

While only a fraction of production jet skis come with air filters, most are equipped with a flame arrestor.

But instead of the air filter, which is intended to clear the incoming air, the flame arrestor serves completely different purposes.

As the name suggests, a jet ski’s flame arrestor is designed to prevent flames from reaching the engine compartment. Flames in the intake can be caused by backfiring, which is a common issue, especially on 2-stroke crafts. These flames can be very dangerous as they can ignite the vapor fumes that have accumulated in the engine bay. In the worst-case scenario, this can end in a huge explosion.

This is why the flame arrestor is an essential safety feature on every jet ski; it stops the flames coming from the engine.

PWC flame arrestors come in many shapes and sizes, and they can also sit in various places.

The flame arrestor is a metal screen mounted inside the airbox in modern jet skis. Some models feature a tubular metal screen that looks like a motorcycle baffle, while others come with a flat arrestor screen.

Basic models like the Sea-Doo Spark have a smaller rounded flame arrestor mounted between the airbox and the intake manifold.

When it comes to 2-strokes without an airbox, they usually have flame arrestors attached to their carburetors.

Contrary to popular belief, a flame arrestor doesn’t significantly reduce engine performance. Because of this, removing it is definitely not recommended!

Although it’s not designed for this purpose, the metal mesh of the flame arrestor can effectively screen some water spray, sand, and other debris. Therefore, it can work as an air filter on a certain level.

On the other hand, it’s a safety feature designed to prevent explosions in the engine compartment.

4. Jet Ski Air Intake Hoses

On modern 4-stroke jet skis, the airbox and the engine are connected by a rubber boot, known as the air intake hose.

In contrast, the airbox of 2-stroke jet skis is often directly attached to the carburetors, so these models didn’t feature intake hoses.

Some models come with fresh air intake hoses that route cold air from the air passages on the top deck into the hull.

How Does a Jet Ski not Suck in Water?

But how does a jet ski not suck water in along with fresh air?

Air intake grills and passages are typically placed on the upper portion of the top deck, far above water level. These inlets are attached to intake hoses that route water into the bottom of the hull. If water accidentally gets into the pipes, it’s drained directly into the bilge, where the siphon system and the bilge pump can easily remove it.

The air intake is also mounted on top of the airbox, far from the bilge water.

The airbox is also designed to keep water away from the engine, while the flame arrestor/air filter can also block some water spray.

These units effectively work together to keep water away from the engine.

What is the Cold Air Intake on a Jet Ski?

One of the biggest drawbacks of a jet ski’s air intake design is that it sucks air from the engine compartment. This air is significantly warmer than the ambient air due to engine heat and the poorly ventilated engine bay.

An OEM jet ski’s air intakes are often restrictive, especially if it features an air filter. This can be an issue, especially on a high-performance modded and supercharged engine that consumes a lot of air.

This is where PWC cold air intake systems come into play. As the name suggests, these aftermarket kits are designed to route cold air into the engine.

These aftermarket intake systems come in many shapes and sizes, but most don’t have an airbox and instead utilize a long fresh air intake hose.

This large diameter hose is usually routed in front of the hull or, even more commonly, into the bow storage compartment. The latter is considered a safer solution as the bow storage is typically watertight.

Besides the hoses, these kits usually feature an oversized air filter made of a stainless steel mesh screen. Since it doesn’t feature cotton like automotive air filters, it doesn’t absorb water and allows the engine to breathe.

These kits come with stainless steel hose clamps and joiners to assemble the system. On supercharged jet skis, the air intake hose clamps directly to the supercharger.If you want to learn more about cold air intake systems and their installation process, don’t miss this great tutorial video:

Other kits feature a specifically-formed intake duct channel instead of afresh air intake hose. This unique feature looks like a long narrow airbox.

For example, this kind of performance air intake kit is offered for Sea-Doo Spark models.

A cold air intake system feeds the engine with a lot of cool fresh air resulting in higher efficiency and slightly more power.

If you are installing some other performance mods, in most cases, you will need a cool air intake system or at least a performance air filter to serve the increased air consumption.

The latter is a much simpler system as it only features a large metal filter and a short air intake pipe. Although this kit also lets the engine breathe easier, it still consumes the warm air from the engine compartment.

Takeaways – How Does a Jet Ski Air Intake Work?

How does a jet ski air intake work? – As a takeaway, we have described the process in detail:
  1. Jet skis suck fresh air into their hull through air intake passages. These intakes are typically mounted on the front of the top deck, around the handlebar neck, or under the front portion of the saddle.
  2. Fresh air is routed into the bottom of the hull via fresh air intake hoses. The main idea behind this design is to keep water out of the engine and the air intake. If water accidentally enters these air passages, the hoses drain the water directly into the bilge.
  3. A jet ski’s air intake system typically features an airbox mounted inside the hull. The airbox features a flame arrestor and sometimes a marine air filter depending on the model. The flame arrestor is designed to stop flames from the engine while the air filters clean the incoming air.
  4. Air is sucked into the airbox, which routes it into the engine through the air intake hoses. A hidden benefit is that it helps keep water out of the engine due to its design.
The drawback of OEM jet ski air intakes is that they consume warm air from the engine compartment.

If you want to feed your engine with cool fresh air, you can choose from many aftermarket cold air intake systems that route the outside air directly to the engine.