Why Jet Skis Overheat and What You Can Do

Spending time on a jet ski, or a personal watercraft, can be an incredibly fun activity. At least, it is plenty of fun until something goes wrong. One of the issues you may experience while jet skiing is overheating of the engine. This can be dangerous as it can damage the motor and could leave you stranded in the middle of the water without help. 

Why do jet skis overheat and what can you do? Jet skis can overheat for a variety of reasons:

  • Cooling lines or impeller system are damaged 
  • Outlet holes are clogged or blocked 
  • Incorrect placement of gaskets
  • Running jet ski engine out of water

It shouldn’t take you long to fix these problems with some minor maintenance and repair techniques, but if you are unsure what to do, take it to a jet ski or boat repair. Check to see if you can identify that any of these problems have occurred and make alterations to fix. 

You don’t want to run into problems when playing on your jet ski, but if you do find that the personal watercraft is overheating, check to see if there are any problems related to blockages or placement of tools. Let’s go into more detail about how this overheating can occur and the steps you will need to take to fix this problem.

Overheating Jet Ski Causes 

When using your jet ski, there are multiple situations in which your jet ski can overheat. Different brands of watercraft will operate differently, but there are some general scenarios that can cause the overheating of a jet ski. These reasons include: 

1. Circulation of Water in Impeller System 

Many personal watercrafts operate by running water through an impeller system to cool the engine. This means that they must take in water from the lake or ocean you are riding in to pass through the engine. Impellers are rotating devices that are used to increase the movement and pressure of water to the engine. 

There are cooling lines that are connected from the impeller system to the engine for proper water flow. If the cooling lines in the impeller system are blocked or do not circulate water properly, then the water will not be able to run through the engine. 

Some potential problems with these cooling lines include: 

  • Leaks
  • Holes
  • Cracks

If any of these are present in the lines, the water will not be able to flow successfully to the engine. If the cooling lines are fully functional, there could be a problem with the impeller itself. The flow of water may also be affected if the impeller is damaged, rusty, or corroded. This will require replacement. 

2. Outlet Hole Blockage 

Another issue could be with the outlet hole. After the water has passed through the impeller system and through the engine, it must exit somewhere. When you see water coming off the back of the jet ski, this is the outlet hole. If water does not come out of this hole, the water passing through the engine will have no way to be released. This can also cause overheating. 

Water may not be coming out of the outlet hole because it is blocked. The stream should be consistent. Any inconsistencies or no movement at all suggests the line needs to be cleared. There are many things that could cause build up, most related to the environment you are jet skiing in. If you launch a jet ski from the beach, you may experience a buildup of sand. Make sure you understand how shallow you can run your jet ski by reading our post.

If you do not take the best care of the jet ski in cleaning it after being in water, algae, plant life, and other bacteria could grow and create a blockage in the outlet hole. This will prevent the cooling system from running its cycle. 

3. Incorrect Gasket Placement 

Gaskets are components used to act as seals for jet skis. These seals are very important to the function of internal workings on a jet ski. Having well-functioning gaskets is crucial to optimal engine performance. When the seals are not placed on correctly or are worn out, they may cause oil leaks and lead to overheating.

When the engine is not able to function properly and receive the necessary lubrication and cooling it needs, it is susceptible to overheating. Checking the seals when you purchase your jet ski or periodically for preventative measures can prevent these problems from arising. 

4. Running Jet Ski Out of Water 

Because jet skis require the water they perform in to keep the engine cool, running a jet ski out of water will put a lot of pressure on the engine and will definitely cause it to overheat if left on for too long. If you do need to run the engine for any reason outside of water, it should only be for a few seconds. Any more than this amount of time could lead to greater damage. 

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How to Fix an Overheating Jet Ski

Now that you know the causes of a jet ski overheating, you need to know how to fix these problems. Most of these you should be able to do on your own. If you are still experiencing trouble, consult a jet ski repair. These are the ways in which you can fix an overheating jet ski: 

  • Replacement: In some situations, including problems with cooling lines and impellers, you may need to replace them if they are damaged. You should identify what areas are damaged and put in new ones correctly to fix the issue. 
  • Cleaning: Cleaning your outlet hole and keeping your cooling lines clear will allow for full function of the engine and keep it from overheating. This is also a preventative measure you should take periodically to keep blockages from happening. 
  • Maintenance and Prevention: Now that you know the causes of overheating, the care and cleaning you engage in should keep overheating from occurring. Make sure that there is no damage to any parts of the jet ski and check the condition of certain mechanisms to see if they are on the borderline of breaking. 
  • Proper Configuration and Placement: When you put new pieces and parts on the jet ski, specifically related the engine, you must make sure that they are placed on properly and secured. Anything that is loose may cause leaks, and completely incorrect placement will prevent proper functioning. 

Paying attention to all of these areas will not only fix the problems associated with your overheating jet ski, but they can prevent problems from happening in the future. These fixes are also not very time intensive. You should have your jet ski up and running again in an hour or two if you are able to easily identify the problem. 

Keeping Your Jet Ski From Overheating 

If you keep your cooling lines in great condition, keep your outlet hole from being blocked, make sure all your parts are placed on correctly and tightly, and try not to run your jet ski when it is out of water, you will avoid problems with overheating. These are relatively easy problems to fix and avoid! It is much better to take preventative measures in keeping your jet ski parts up to date. 

Jet skiing can be so much fun, and you do not want overheating of your engine to be the thing to slow you down. Hopefully, you can use this guide as a tool to make quick fixes for engine overheating, and then this information will help to prevent issues from occurring in the future! 


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Tim Conner, M.D.

Tim Conner, M.D. started boating in 1974. He has been involved in recreational boating continuously since then. Dr. Conner has been active in boating and watersports safety education for decades. He rode his first jet ski in 1997, and rejoined the personal watercraft arena in 2012 with a Sea-Doo GTX 155, followed by 2 supercharged SeaDoos. Scuba certification came in 1988, and he and the family have traveled the world snorkeling and scuba diving for decades. The family has recently taken up paddle boarding. Click the photo for a lot more.

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