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Why Is Your Jet Ski Overheating? [And How to Troubleshoot It]

Home/News/Why Is Your Jet Ski Overheating? [And How to Troubleshoot It]

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If the temperature of your jet ski’s engine rises significantly, a warning indicator appears on your dashboard. Moreover, very often a beep code will also alert you of the problem.

There could be many reasons why your jet ski is overheating, but in any case, you need to troubleshoot it immediately.

Keep in mind that improper cooling can damage the engine’s internal components in many ways!

We, at JetDrift have compiled the possible reasons for why a jet ski might overheat, and how to fix these issues.

Why is Your Jet Ski Overheating?

The most common reason why a jet ski overheats is a clogged cooling system or cavitation in the pump. Other possible causes are the lack of engine oil, clogged oil system, or carb issues. It’s not just the engine, but the jet ski’s exhaust system and the intercooler are also prone to overheating, as these parts are also cooled with raw water.

Additionally, your jet ski can overheat if you run it incorrectly out of the water.

Let’s take a closer look at these issues and how you can avoid them.

Reasons Why a Jet Ski is Overheating

Clogged Cooling System

The leading reason why so many jet skis overheat is arguably a clogged cooling system.

Sand, mud, or small debris can easily get into these systems, causing a jam. If the cooling water is blocked somewhere, the engine starts to overheat fairly quickly.

That’s why you have to inspect your jet ski carefully. In many cases, only the jet intake is clogged. Take a closer look at the intake area and clean it if needed.

Also, check the entire cooling system for leaking or other damage.

Beyond checking, you may also want to flush these systems with raw water. Attach the garden hose to the flushing port and run the water according to the manufacturer’s instructions.

Don’t forget that if you have a Sea-Doo that features a closed-loop cooling system, it’s exhaust and intercooler still use external water for cooling.

Cavitation

Another reason why so many jet skis overheat is because of cavitation.

Simply put, cavitation is when bubbles form and accumulate in the pump around the impeller.

Since the cooling water comes from the pump on jet skis, if your jet ski is overheating, you have to thoroughly inspect the pump.

The leading reason for cavitation is a damaged or improperly sized impeller.

So, if you use an aftermarket impeller make sure it fits to your engine perfectly, especially if you’ve made any modifications on your jet ski for higher performance.

It’s important to know that increased performance makes a new impeller necessary in many cases.

Cavitation is a serious issue as it can damage the pump housing and the impeller. Additionally, it can significantly reduce water flow to the cooling system, and this leads to lower performance.

You can notice cavitation when the engine RPMs are high, but your jet ski still moves slowly. The reduced power probably comes from lower pressure in the pump, caused by cavitation.

In this case, you may want to remove and inspect the impeller carefully. In some cases, you can adjust it yourself, but in cases of major damage you will need professional help or may even have to replace the impeller.

Don’t forget to check the wear ring as well, especially if you notice any impeller damage.

Lack of Oil

4-stroke engines need an appropriate amount of oil in their engines to run properly.

If your jet ski overheats, one reason for this could be low oil pressure in the engine. First, check the oil level with the dipstick and refill if necessary.

If the oil level is correct, the oil pressure can still be low for many other reasons.

A clogged or broken oil filter, contaminated oil or other malfunctions in the oil injection system may cause low oil pressure as well. You should change the filter and the oil if necessary.

If you have a 2-stroke jet ski, make sure the oil pump works properly and you’re using the right oil.

If your craft runs on premix, pay attention to the right ratio: for better lubrication, you can’t go wrong with a ratio of 40:1. It’s easy to mix because all you do is add ½ quart of oil to a 5-gallon gas can.

Gaskets

Broken or wrong sized gaskets can also lead to overheating on a jet ski, especially on an aged model.

Check all of the gaskets carefully. If you see any issues, best practice is to invest in a complete gasket kit and replace all of them.

In many cases, a wrong head gasket is the source of the error. Unfortunately, replacing the head gasket on a jet ski can be tricky, which means you will need some skills and the right tools.

We recommend that you always use OEM gaskets, hoses and other parts for your jet ski, as the wrong sized gaskets can also obstruct water flow, which can result in poor cooling.

Before you pull the engine out, it’s wise to check the compression. It should be the same in all cylinders and match the manufacturer’s recommendation.

Other Issues

Although these are the most common problems, there could be many other reasons why a jet ski would overheat.

Here are some additional tips on what to check out on your craft:

– If you have a Sea-Doo, check the coolant level, and refill if needed.

– Check the water exit hose of the cooling system. Is it kinked or blocked?

– If you have a 2-stroke jet ski, check the carbs. They may be clogged and running lean.

– If your jet ski was modified, the increased performance can also cause overheating.

– Don’t forget that even the temp sensors can be wrong. If you can’t find the source of the error, they may also be worth checking.

– It could also be a system error that causes the dashboard to give an incorrect signal.

– Beyond the engine and the exhaust, the starter can overheat as well. If the engine doesn’t start, don’t crank it any longer than 10 seconds as you may overheat the starter.

If you can’t determine or fix the error, it’s recommended that you take your jet ski to your dealer or a reputable service shop.

Running Out of the Water

It’s also important to know that your jet ski can overheat if you improperly run it out of the water.

To do it right always keep these rules in mind:

NEVER run a jet ski longer than 15 seconds without supplying water.

– Once you’ve attached a garden hose to the flushing port, start the engine first before you open the tap.

– Don’t run the jet ski any longer than 2 minutes out of the water, even if it’s attached to the hose.

– Make sure there is decent water pressure in the hose, but NEVER use high-pressure water to flush the jet ski!

Keep the RPMs low if you’re running your jet ski out of the water, as high RPMs can quickly overheat the engine.

– After flushing, first shut off the water, and immediately after, shut down the engine.

– Don’t forget to remove the connect adapter from the flushing connector, as it can lead to the engine overheating as well.

In some cases, the “jet ski overheat fault code” appears during your ride, but not when it’s attached to the hose.

This is because while on the hose the jet ski’s engine remains cold as there isn’t much power. But this could also be a clue for a clogged jet intake.

How to Fix an Overheating Jet Ski

To fix an overheating jet ski you should shut the engine down, and tow it back to the dock. First, inspect and clean the jet intake, pump and the cooling system. Attach it to a garden hose and flush the cooling system for 2 minutes. If that doesn’t help, check the oil level and injection system (or carbs), gaskets, and the temp sensors.

This is how to troubleshoot an overheating jet ski in a nutshell, but here is a step-by-step guide for what to do if your jet ski overheats during your ride:

Turn Off the Engine

If you notice that your jet ski is overheating, you have to shut down the engine immediately. Wait 3 minutes and try turning the engine on.

In many cases, this trick helps to eliminate the fault code.

Return to The Dock/Shore

If your jet ski has a serious issue, you probably won’t be able to restart the engine at all. But even if you can and still see the fault code, it’s highly recommended that you not operate it.

This is because if you ride at higher speeds without efficient cooling, it may result in serious engine damage.

Best practice is to tow the craft back to the dock with another jet ski or even a boat.

Check and Clean

When you put your jet ski on the trailer, first check the jet intake for debris. If it looks clean, hook the jet ski up to a garden hose and flush it for 2 minutes.

In many cases, the cooling system is just clogged with sand or rocks, which can be flushed out this way.

Fixing an Overheating Jet Ski

If the fault code is still present, try to read it by attaching a computer to your jet ski.

To do this, you will need special a diagnostic cable and software like MEDS or CandooPro. These are usually available in packages.

Reading the fault code can help you learn more about the issue.

Additionally, it is also recommended that you look at these parts:

– Check and refill the oil if needed (or make sure you’re using right mix ratio)

– Check the whole oil injection system (change the oil if needed)

– Adjust the carbs

– Replace the hoses and gaskets

– Replace the head gasket

– Replace the temp sensors

And it’s highly recommended that you carefully read the owner’s manual before servicing your jet ski yourself!

How to Avoid Overheating Issues

As they say, prevention better than the cure, so here are some vital tips on how to avoid overheating issues.

– Never operate the jet ski in shallow water.

– Don’t beach your jet ski, you should anchor it instead.

– Flush it after ever ride carefully with fresh water.

– Don’t overlook the regular maintenance and only use OEM parts.

– Check the oil level, impeller, and wear ring regularly.

– Avoid modifications.

Conclusion

There are many parts on your jet ski that are prone to overheating. These are mainly the engine, exhaust system, and the intercooler.

Moreover, the starter can also overheat if you crank your engine for more than 10 seconds.

Jet skis can overheat for many reasons, such as:

– Clogged jet intake or cooling system

– Cavitation (damaged impeller or wear ring)

– Lack of oil or clogged oil injection system (or carb issues)

– Cracked or broken gaskets

– Wrong temp sensors

– Improper service or modifications

If you want to fix your jet ski yourself, it’s recommended that you check these parts. In case you can’t determine or troubleshoot the issue, you can still take your jet ski to a dealership or a service shop.

Also, don’t forget to refer to the owner’s manual every time before starting to service your jet ski!

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