Why Won’t My Jet Ski Start? Main reasons your jet ski isn’t starting

It can be concerning if your jet ski won’t start when you turn it on or press the gas. If your jet ski isn’t starting, it’s important to find the cause instead of continuously hitting the gas, as this could damage it further. In today’s article, I will review the main causes of a jet ski not starting.

Why is my jet ski not starting?

The main reason your jet ski is not starting is because of a dead battery, stale fuel, faulty spark plug, water in the engine, clogged drive shaft, and electrical issues.

Dead battery

The main reason a jet ski won’t start is because the battery is dead. This usually occurs when you take your jet ski out to the water for the first time after winter. There are two main ways to tell if the battery is dead.

If you stick the key in the jet ski to turn it on and nothing lights up, then your jet ski is probably dead. If you turn on the jet ski and the gauges light up, but there is a bunch of clicking sounds, this is a sign that your battery is very low and doesn’t have enough power to start up the jet ski.

In order to check the status of your battery, you should hook it up to a charger. If the battery won’t hold a charge, then you will need to replace it. If your battery is able to register a charge, it can be revived. However, it is important to slowly charge it so that you don’t fry it. I suggest not charging more than 3 amps, which can take up to a day to get your battery back to full charge. While it might be frustrating to wait this long, it will help the longevity of your battery.

The main reason a jet ski battery dies is because you didn’t have it on a trickle charger over the winter. This is very important because it prevents your battery from getting drained.

Also, some people don’t realize that a good battery usually only lasts for around 4 years or so. Even if you keep your jet ski in good condition, you will likely need to replace your battery two or three times in its lifetime.

If your looking to buy a battery, you can check out my article on the best jet ski battery

Stale fuel

Another common reason a jet ski won’t start is because there is stale fuel in the engine. Similar to a dead battery, this is also common when you take your jet ski to the water for the first time after winter. If your jet ski is not going to run for a couple weeks, it is important to drain the tank of fuel.

When fuel sits in the tank for a while, it will likely take on water and lose its consistency. Also, sitting fuel can cause corrosion in your jet ski’s interior.

You can add fuel stabilizers to your tank to help improve the efficiency of your fuel. This can help prevent corrosion and also give your jet ski better mileage. You can learn more in my guide on the best fuel additives for jet skis

Corroded spark plug

A deteriorated or faulty spark plug is also a common reason why a jet ski won’t start. The spark plug’s job is to create a spark that fires up the fuel in your engine. If the spark plug is corroded, it won’t be able to spark the fuel to fire up the engine.

If your jet ski’s spark plugs are corroded, your jet ski will probably still start up initially, but once you hit the gas the engine will cut off. It can also cause your engine to make clicking sounds.

You should check your spark plugs every couple of months to ensure they are in good shape. If there is a brown tint on them or any sort of corrosion, you should replace them. Luckily spark plugs are pretty cheap and easy to replace.

You should replace your jet ski’s spark plugs every year or so, and ideally you should do it after your jet ski has been sitting over the winter. If you don’t regularly replace the spark plugs, it can also cause your jet ski to have low compression

Clogged drive shaft

Your jet ski’s drive shaft is where water shoots through the bottom of your jet ski and is then shot out by the impeller. It is fairly common for dirt, rocks, sticks, and ropes to get caught in the drive shaft. These items can also get caught in your impeller.

While this usually just causes your jet ski to go very slow, extreme blockages can cause your jet ski to not start. If you suspect this is the cause, you should carefully inspect the drive shaft to see if anything is stuck.

In the future, you can help prevent this problem by not riding your jet ski in shallow waters or after a big storm when there is a lot of debris in the water.

Water in the engine

Another reason your jet ski won’t start is because water got in the engine. While most jet skis are engineered to withstand a little water in the interior, large amounts of water can cause serious damage.

This is usually caused when you don’t store your jet ski properly, or if you flip it over and it stays upside down for an extended period of time.

If you suspect there is water in your jet ski engine, it is very important that you don’t run it, as this can cause more damage.

You can learn more in my article on how to fix a flooded jet ski.

Electrical problems

If you tried all of the solutions above and your jet ski still isn’t starting, your jet ski probably has some electrical or engine problems. Unless you are a well versed handyman, you will probably have to bring your jet ski into a mechanic. However, you can lift up your jet ski seat and at least make sure that everything is connected and that there are no loose cords.

Some of the main electrical/mechanical issues that will cause your jet ski not to start are:

Faulty start relay: This is usually the problem if your jet ski makes a loud thud sound when you press the gas. You will likely need to replace the start relay if this is the cause. Start relays need to be replaced every 3-5 years.

Blown fuses: If there is a burning smell or smoke coming from your jet ski when you try to start it, there is a chance there is a blown fuse. This is a pretty complex thing to fix so I suggest taking it to a mechanic to ensure it is properly fixed.

Rusted cables: If you ride your jet ski in saltwater, your jet ski is very susceptible to corrosion. The saltwater can cause your cords and your engine to develop rust, which can eventually cause your jet ski not to start. You can help prevent this by frequently flushing your jet ski with freshwater after you use it.

There is also a chance that your jet ski is just old and at the end of it’s use. While it may seem shocking, many jet skis only last for 300 hours


I hope this article helped explain the main reasons why your jet ski is not starting. While some of the issues are easy fixes, some might require you to take your jet ski to a mechanic.

You can help avoid these issues by taking proper care of your jet ski and properly winterizing it.
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