Your Waverunner could be smoking for any number of reasons, the most common of which being an overfill of oil causing the oil to get into the airbox and on the air filter. This is a straightforward fix, and you can have your Waverunner back in top condition in no time. A little smoke at start up is common and usually quickly clears as engine warms up.

If you’re the owner of a Yamaha Waverunner, you’ve likely run into the problem of smoke coming off the engine block at some point in time. While it’s a fairly common problem to encounter as a Waverunner owner, it’s no less concerning to see your Waverunner giving off smoke and not working properly.

Why Does my Waverunner Smoke?

The most likely reason your Waverunner is smoking is from an overfill of oil that is causing it to leak into the air box and air filter. The engine of a Waverunner uses a fuel injection system, meaning it takes gasoline and motor oil from separate compartments and mixes them in the proper ratio before injecting them into the engine in a 2 stroke jet ski (my post). 4-strokes of course don’t mix oil and gas.

While motor oil is a critical component to keeping the engine properly lubricated, it can be detrimental to overfill your oil tank. The proper time to measure the oil level in your tank is when the engine is at operating temperature, generally after about 15 minutes of use.

Once the engine is warmed up, measure the oil level using the dipstick and make sure it reads about midway between the full and the empty markings.

If your oil level is any higher than this, you run the risk of it leaking out into other parts of the motor while running your Waverunner. This is where you run into the problem of your Waverunner smoking. Oil can also foam when over-filled, leading to internal damage.

A common place for overflowing motor oil to end up is in the air box and on the air filter. When this happens, you’ll start to encounter the issue of the oil burning off and creating the smoke you’re seeing.

This issue is also not uncommon in new Waverunner’s. New owners frequently mention encountering this problem shortly after purchasing their Waverunner from the dealer. While dealers are supposed to be trained experts on how to take care of these machines, some are better prepared than others.

While this is a fairly common problem, you should be sure to address it as soon as possible. An underperforming air filter can cause other issues for your Waverunner and will hinder the machine’s overall performance.

How Can I Change the Air Filter?

For those with a little technical know-how and a can-do attitude, changing the air filter on your Waverunner can be a reasonably easy process. Regular inspection of the air filter and air box can also be a great way to ensure that your Waverunner is running in top condition. For those with the motivation to tackle this project themselves, follow these steps:

  1. Remove the seats. Removing the seats is the first step to accessing anything regarding the engine, and the air box and air filter are no different.
  2. Remove the air filter case cover screws and slide the locks open. These parts hold the cover to the air box securely in place during operation. Once removed, the air box cover can be taken off, making the filter itself accessible.
  3. Remove the air filter and inspect for oil, debris, or wear and tear. This is where you’ll find the most likely culprit for your Waverunner smoking. If the oil is overflowing out of the oil tank during operation, you’ll likely see a buildup on the air filter. If this is the case, you’ll want to replace the filter and wipe out any oil buildup within the air box. Additionally, you should consider replacing the filter every 2 years or after 200 hours of operation.
  4. Reinstall the air filter case cover.
  5. Reinstall the seats.

It should be noted that someone without the know-how or some level of experience working an engine air filter should likely not attempt to replace the air filter on their own. While it’s a fairly straightforward process, getting something wrong could cause damage to your Waverunner that’s simply not worth the risk.

For a step by step walkthrough on how to replace the air filter in your Waverunner, check out this video.

What Are Some Other Reasons my Waverunner is Smoking?

Though an overfilled oil tank is the most common reason for your Waverunner to be smoking, there are a number of other potential culprits. Some other reasons your Waverunner could be smoking include bad gas, problems with the fuel injector, fogging oil from winterization (as I recommend in that post) or a failed head gasket. While each of these issues vary in seriousness, they can all cause smoke in your Waverunner and should be addressed quickly.

  • Bad Gas
    This is a fairly innocuous problem that can occur in your Waverunner and is the only issue listed in this article that doesn’t require an immediate fix. Imperfections in the gas can cause smoke to occur, giving off the impression that something is wrong with the machine.

    The best way to tell if the smoke is caused by lousy gas and not something more serious is if the Waverunner displays no drop in its performance. If your Waverunner is performing in top condition while also giving off smoke, it’s likely just a bad batch of gas.
  • Problems with the Fuel Injector
    Because your Waverunner operates on a mix of gasoline and motor oil, many models will feature an injector system that pulls from a gas tank and an oil tank to create the correct ratio of mix. If the injector system isn’t working correctly, it could be feeding too much oil into the engine which in turn could be causing the smoke you’re seeing.

    If this is the case, you can either get the injector system repaired or replaced, or you can remove the system entirely and simply premix your fuel. The latter option is a bit trickier, and you shouldn’t attempt this without the proper know-how. You’ll also want to be sure that you’re getting the correct ratio on your fuel mix before adding it to the gas tank, as you’ll just be replicating the problem if you get it wrong.

    If the problem with your Waverunner smoking is caused by a bad fuel injector system, you’ll also want to inspect your spark plugs, as some of these were likely fouled up by the faulty injector system. Be sure to replace any that were damaged by the excess engine oil coming from the injector system.
  • Failed Head Gasket
    In this case, you will either need to tackle this by watching some videos, buying a maintenance and repair guide, or taking it to a shop.

Another potential culprit for your Waverunner smoking is actually not smoke at all, but instead steam. This can be determined by how long the smoke/steam lingers after being emitted from your Waverunner. While smoke will linger for a bit, steam tends to dissipate rather quickly.

If it’s steam, your Waverunner could have a failed head gasket. This will allow cooling water that is usually pumped throughout the engine to enter the combustion chamber, which will result in steam coming from the exhaust. While some level of steam is to be expected, enough to cause you to stop running the engine is likely from a blown head gasket. 

To check this, you’ll need to run a compression test. If it’s reading significantly less than 90 psi or showing one cylinder considerably lower than the others, then it’s likely a failed head gasket.

  • Burning off cylinder fog or sea foam from winterizing: Run the motor at idle for 30 seconds or so, then gradually add throttle until smoke clears. Don’t start and immediately go full throttle away from dock. It should clear within 60 seconds or so.

Final Thoughts

If your Waverunner is smoking, it could be for several reasons.  The best-case scenario is a batch of bad gas.  That’s the most straightforward remedy, so if performance is not affected, then enjoy yourself.  Maybe it’s time to find a new gas station.