Troubleshooting a Smoking Jet Ski: 8 Causes and Fixes


Perhaps you are a jet ski owner, or you have enjoyed watching the machines buzzing across the lakes, and rivers near you.  Either way, you may have noticed smoke coming from the jet ski. At first glance, you may think there is a major mechanical error, or the jet ski is on fire. The good news is that the jet ski is likely not on fire and there is probably not a major mechanical error.

Why do jet skis smoke? Jet skis will smoke under normal operation if you have a 2 stroke engine. If you have a 4 stroke, smoking is a sign of something being wrong. The color of smoke can tell you a lot about what is wrong with your jet ski and point you in the right direction of a fix.

The most common causes of smoking jet skis are.

  • An overfill of oil
  • Bad gas
  • Problems with fuel injector
  • Failed head gasket
  • First run of the season
  • Normal 2 stroke operation
  • Bad Oil Injectors
  • Bad Mix Gas

As you can see, there are many potential causes of smoking jet skis, some are more problematic than others and if you have a 2 stroke jet ski, smoking may be normal, but all of them can be remedied rather easily, either independently or with the help of a mechanic.  In this article, you will learn the top causes of smoking jet skis and easy fixes for the smoking.

Is all Smoke Bad?

When you begin looking at the smoke being emitted from the jet ski, you need to carefully observe where the said smoke is coming from as well as the color of the smoke. This observation is critical to determine the correct fix. 

Location: When noticing smoke, you need to determine where exactly the smoke is coming from. If the smoke is coming from the back of the jet ski, you need to look carefully to determine if it is smoke.  Often, jet skis emit a white mist or fog that can take on the appearance of smoke. This can be from normal operation, and not be a signal of anything bad happening.

If you notice the smoke coming from the side of the jet ski or near the engine, it is likely going to be a light gray or white color.  When it comes from the side of the jet ski such as through an air vent or under the seat, this can be indicative of an actual issue within the engine or components of the engine.

Color:  The color of the smoke can help pinpoint the cause as well as the location.  The typical colors you will see are white, black, or gray.

Color of SmokePotential Cause
WhiteIf you notice white smoke coming from the back of the engine it is likely that you are seeing steam, which can take on the appearance of white smoke. Another cause of white smoke may indicate and issue with your oil that needs to be checked. White smoke can also be telling you that your jet ski is running lean.
GrayThere is a chance that you have oil leaking onto your air box or engine filter.  
BlackBlack smoke can be alarming to see, but it does not mean your machine is about to explode, but it does indicate that you have a problem that needs to be addressed.Typically, black smoke indicates an issue with your fuel.

As a rule of thumb, if you see smoke coming from your jet ski, you need to do a bit of investigating before using the machine.  While it may seem like something that can be ignored until you are done on the lake or river, there is a chance that you could cause significant damage to your machine that will not be a quick do it yourself fix. 

Is it smoke or steam coming from my jet ski? Most jet skis naturally have steam or some smoke coming out of the combustion process. Smoke may be white, grey, or black. Smoke also has a distinct smell verses steam and smoke typically alerts you of something wrong with your waverunner.

8 Causes of Smoking Jet Skis

There are many mechanical situations that can cause a jet ski to spew smoke, while some are minor, some are quite significant and will require your immediate attention to ensure your jet ski remains in working order.  The six most frequent causes of smoking jet skis, in no order are.

  • An overfill of oil
  • Bad gas
  • Problems with the fuel injector
  • Failed head gasket
  • First Run of the season
  • Normal 2 stroke operation
  • Bad oil injectors
  • Bad mix gas

Looking at this list, you can see some are a bit more concerning than others, but all are quite easy to fix if they are caught and addressed right away.  If at any point you are uncertain of the cause of the smoke, it is important that you speak to someone that has experience with jet skis or a certified jet ski mechanic. If you are looking at anything that could potentially damage the engine or innerworkings of the machine you need to have it taken care of. Not only will this provide more time on the water, it will also save you a significant amount of money on repairs.

An Overfill of Oil on your 4 Stroke Jet Ski

Sometimes when you are putting oil into the jet ski, it can be quite easy to accidently overfill the machine. While this may not seem like a huge deal, it can cause a significant amount of smoke and distress to both you and anyone that is watching your jet ski smoke. This only applies to 4 stroke jet skis.

Indicators of Overfill: When you or someone else has accidentally overfilled the oil on their jet ski, the first indicator you will have is likely going to be white smoke. This white smoke will not be coming from the back of the jet ski, it will likely be coming from the sides of the jet ski.  You will also notice the jet ski does not perform as well or for any length of time when it has been overfilled with oil.

Problems with Oil Overfill: It may seem quite insignificant that there is excess oil in the machine, and you may think it will just run out of the machine.  Unfortunately, this is not the case.  When a jet ski is overfilled with oil, it can cause several issues that can ultimately cause damage to the machine.

  • Ruined air filter
  • Damage to spark plugs on the machine
  • Hydro lock engine
  • Potential damage to the engine rods and piston

It is critical that you take the time to ensure there is a proper amount of oil in the machine before taking it out on the water.  You need to remember that oil expands as it is heated, so you do not want to overfill the machine when it is cold. 

Troubleshooting an Overfill

Let’s face it, everyone makes mistakes sometimes and if you have purchased a machine that has been overfilled or you have inadvertently overfilled your machine, you need to know what to do to fix it.  Luckily, there are some quick and easy fixes.

  1.  If you have noticed the machine is overfilled, remove some of the oil before you even start the engine.  This may be a pain, but trust me, it is worth it to save yourself from the headache of other potential fixes.
  2. If you do not notice the overfill issue until after the machine has been run, you will likely need to change your air filter and the spark plugs.  The air filter is relatively easy to change, as are the spark plugs, but if you are uncertain of the proper procedure, make sure you find someone to help you.
  3. If you have been running the machine heavily without stopping to check the source of the smoke or poor engine power, you have likely caused damage that will need to be assessed and repaired by a certified mechanic.  If an overfilled engine has been run at high speeds for a lengthy time with excess oil, you can cause the engine to go into what is called hydro lock. Hydro lock – When you have an excess of water and/or oil in the engine it causes the engine to not turn over. 

If you think you have hydro locked the jet ski, begin by draining the water/oil out and removing the spark plugs.  If you attempt to start the engine after this with no luck, you may need to visit a mechanic because there is a chance internal engine damage has occurred.

  • Damaged engine rods can occur if the engine is allowed to run with too much oil in the machine. When this occurs, the rods tend to slip in the engine and cause the piston to not line up correctly when running. This can cause bent or broken rods. The only fix for this is the replacement of the internal engine workings.

As you can see, oil overfill can cause significant damage to occur to your jet ski. If you think there is any chance at all that your machine is overfilled with oil, stop right away, and check it. While some of the fixes are easy, others will require the help of an expert and will likely be quite costly. 

Bad Gas

Because jet skis are seasonal for most people, unless you live in a location where water sports can take place year-round, there is a chance you have bad gas in the machine. If you have bad gas in the machine, you will likely notice white or gray smoke coming from your jet ski.  You will also notice the machine may be having difficulty operating correctly. As with anything out of the ordinary, stop the machine and check it out.

Problems with bad gas: The most common problem you will face with bad gas is a poorly operating machine.  You may notice it does not accelerate the way it should, and you may notice smoke coming from the machine.

What makes bad gas? Bad gas can be caused by a couple of different things.  Because you are working with a watercraft, there is a possibility that water has gotten into the tank.  There is also a chance your gas has expired. It is common to keep gas on hand for different machines that use it. While this is handy, you may run the risk of using expired gas. 

Unfortunately, there is not an easy way to determine if you have water in the gas or expired gas, however it is a simple fix, given a bit of time and slight mechanical ability.

Tip: Always use fuel stabilizer to treat your gas every tank. This will give your gas a longer shelf life and can keep your jet ski running problem free.

Troubleshooting Bad Gas

Again, you will not be able to tell the gas is bad with any obvious signs, however there are a couple of things you can do to determine if the gas is bad.

  1. Please remember gas is extremely dangerous to work with, so you need to be extra careful when handling this problem. To remedy your bad gas, you will need to drain your fuel tank into a spare fuel container and dispose of properly. This will remove all traces of either water or bad gas.  Replace the gas with new premium gas and see if that resolves the problem.
  2. If you are still having issues, you may need to enlist the help of a certified mechanic because there may be water in the lines or debris that has built up from the use of bad gas.

When you are storing gas for the season, make sure you include stabilizer in the gasoline.  This will help ensure it is okay to use the following season.  If you forget this step, get rid of the gas, and get new gas for your machine.  It is worth the extra cost to ensure you do not have to spend the time or money to drain the tank.

Fuel Injector or Carburetor Problems

Another cause of smoking engines can be the fuel injectors. Fuel injectors work overtime in engines and can easily become dirty over time. When your fuel injectors become dirty, they can cause the jet ski to misfire or smoke. If you think the fuel injectors are bad in your jet ski, it is an easy fix.

Troubleshooting Fuel Injectors or Carburetors

The first thing you need to do is determine if the fuel injectors or carburetor is dirty. If they are dirty you will need to clean them.  The easiest way to determine if your fuel injectors are dirty is to remove them and see if a mist will go through them. If liquid is not passing through, you will need to clean them.

  1. You can try adding a fuel injector cleaner directly to your gas tank.  Make sure you are adding an injector cleaner that is specific to your machine to avoid any damage. I like to run Seafoam every few tanks as well to keep my injectors and fuel system clean.
  2. If adding an injector cleaner does not work, you can choose to clean your fuel injectors manually with a special cleaner after you remove them from the machine.  This is a more time-consuming method but may be necessary if they are especially goopy and clogged.
  3. Take the machine to a certified technician to have the injectors cleaned.
  4. If you have a carburetor on your jet ski, you can simply take it apart and use some carb cleaner to clean it.

The fuel injectors and carburetor are both relatively easy fixes, once you determine they are problematic. How you choose to handle the cleaning is completely up to you. Typically, if you use high quality gasoline and injector cleaner in the tank you will resolve the problem without the hassle of any mechanical work or fees.

Failed Head Gasket

The head gasket is a critical component of a jet ski engine.  It is responsible for providing a seal that eliminates the risk of coolant or oil leaking into the cylinders. If the head gasket goes bad, as it sometimes will, you will run into engine problems with your jet ski.

Indicators of failed head gasket: You may be wondering how you know the head gasket has failed on your jet ski. Remember the purpose of the head gasket is to provide a level of compression that will not allow water to leak into the cylinder. If water is leaking into the cylinder you may notice the jet ski lagging at take off or smoke coming off from the engine. 

Problems with failed head gasket: When water gets into the cylinders you can begin to experience other mechanical problems that are costly to repair. 

Troubleshooting Failed Head Gasket

You may need to enlist the help of a certified repair technician to check the head gasket, but if you are comfortable navigating the engine of your jet ski, it is something you can do on your own as well.

  1. Examine the head gasket for any warping or cracks.  If you notice either of these things, it is indicative of a weak seal, which can be causing water to leak into the cylinder as well as weakened compression.  This means you will need to replace the head gasket.  To ensure you purchase the proper equipment, check the owner’s manual for specific part requirements.
  2. If you have replaced the head gasket on your own and are still experiencing problems, you may need to take it to the repair shop.  Sometimes there are small ridges or bends that cannot be seen by an untrained eye. The repair shop will be able to diagnose any potential issues as well as correct them relatively quickly and easily.

The head gasket is a critical part of a jet ski engine and needs to be check regularly for cracks or warping to ensure it is offering the correct level of compression to the engine.  If there is a lack of compression, serious damage can occur to the engine.

First Run of The Season

If you have ever gotten on your jet ski after placing it into storage for the winter, you may notice a large amount of white smoke coming from the back of the jet ski.  This is not something you should be overly concerned with.  In fact, it is quite common during the first run of the season. 

Causes of smoke: The “smoke” in question is likely not smoke at all.  It is likely cylinder fog or sea foam that is escaping after being winterized.  It is more than likely a fine water vapor that occurs when the hot exhaust is cooled by water running through it.

Effects of “smoke”: Lucky for you, there are no negative effects for this type of smoke or steam.  It is something that is quite common and will resolve on its own.

Troubleshooting

There is nothing that needs to be done to troubleshoot this issue after a few minutes on the water, you should notice a lessening of the white smoke as any residue is burnt off from the process of winterizing.

2 Stroke Jet Ski

2 stroke jet skis will naturally smoke. They will either have mix fuel or be oil injected. This type of engine will burn the oil through the combustion process vs a 4 stroke that will keep the oil in a sump and not burn through it.

Oil burns a darker blue color, so this may just be the natural process of combustion on your jet ski.

Troubleshooting

Typically, this will have a sweeter smell and be consistent with the running of your jet ski through its life. There is nothing else to do or work on.

Bad Oil Injectors

A 2 stroke ski may have an oil injector system. These systems are known to fail and many riders will convert to an oil block off plate and use mixed gas to always ensure their jet ski doesnt break down.

Bad oil injectors can either put too much oil in the combustion process or too little. The latter is the usual and typically you will fry your motor.

If you have an oil injected ski and you notice your waverunner smoke is no longer blue and starts smoking white, this may mean your oil injector is bad.

Troubleshooting

One way to check to see if your injectors are still working is to see if your oil tank is going down as you ride. If you notice you are going through more oil or less oil than usual, it may be time to remove your oil injection system as they are known to fail.

You can spend the time and money to check to see if your injector is still working, but many just install an oil block off plate and use mixed fuel to ensure their watercraft is getting proper lubrication.

Here is a block off plate that will work with many Polaris, Seadoo, Kawasaki, Yamaha, and Tigershark jet ski models. Simply remove your oil injection system and install this plate and 2 bolts and you are done.

Keep in mind to always mix your fuel after this as you won’t have oil if you don’t.

Bad Mix Gas

Jet ski manufacturers will tell you what ratio of mix of gas to put in their engines. Sometimes due to human error, you may mess up and either use too much or too little oil in your mixture.

If you are burning more blue smoke than usual, and your ski is sluggish, this is a sign of too much oil.

If you are burning white smoke and the ski is peppy, this may mean your mix has too little oil.

Always ensure the proper mix so you don’t do permanent damage to your jet ski.

Troubleshooting

To troubleshoot this, look to see what color of smoke is coming out of your exhaust.

  • If it is blue, you may add a bit more fuel to get a proper mixture.
  • If white, try adding some more oil.

If your fuel tank is low don’t try and mix fuel in your jet ski tank, just make a new mixture of gas in a 5 gallon can so you can take the guesswork out of the proper mixture.

Final Thoughts

Smoking jet skis can be caused by many things; however, most are relatively easy to repair and are quite inexpensive.  If you notice your jet ski is smoking, do not just write it off as a temporary thing and continue riding.  Take the time to inspect your jet ski to determine what the root cause is.  Taking this time at the beginning will save you time and money down the road.  Again, if you are not confident in your ability to diagnose and repair the jet ski, take it to a professional.  A misdiagnosed cause of smoking can cause unnecessary damage to your machine.

Eric

I have been an avid boater / jet ski fanatic since I was a kid.

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