Jet Ski Won’t Start? Here Are 4 Common Causes

by John Wren
A white jet ski mounted on a trailer, which is on a beach ramp, with sand and the ocean in the background.

Who doesn’t love a day out on the water on their jet ski? But no one wants to take out their jet ski only to find it won’t run. Below, we examine the common causes of why a jet ski won’t start and offer some simple solutions to help you get back out on the water quickly!

Weak or Expired Battery

In most cases, the problem lies with the jet ski’s battery. Your jet ski may not even click, or the motor may not come close to turning over when you hit the ignition. These situations are likely due to a dead, expired, or weak battery.

This can be both good and bad news. If it’s just a dead battery and there’s nothing functionally wrong with it, a quick charge will fix the issue. If you’ve already charged the battery and it’s still weak or dead, the unit is likely broken or expired, and you’ll have to replace it. To maintain your jet ski’s battery, you’ll want to employ battery life best practices for boats, such as doing regular inspections and cleaning the connections to remove corrosion.

Defective Spark Plugs

Another common cause for a jet ski that won’t start is defective spark plugs. As with cars and other vehicles, spark plugs are integral to the function of jet skis and are the ignition parts that start watercraft and get their engines running.

If your jet ski spark plugs fail, it’s likely that they’re old, they’ve expired from use, or they’ve somehow sustained damage. Either way, the best solution is to simply replace them with new plugs, which are easy to find and straightforward to install.

Faulty Starter Relay

If it’s not the battery or the spark plugs of the jet ski, boaters will also want to check their starter relay. The starter relay is a crucial component of a watercraft’s starting system. It’s a remote switch that transmits power to the starter motor from the battery to turn the engine on.

Without a properly functioning starter relay, the motor won’t start, and owners will only hear a click when they try to turn over the engine. If you hear one click when you try to start the jet ski motor, you probably have an issue with the starter relay. You should have it checked, as it may need a replacement.

Bad Fuel

Jet ski owners can’t overlook the importance of quality fuel for their jet skis. For those who only use their jet ski sparingly and have it sit with a tank full of fuel for weeks or months, the stale fuel can cause problems.

It’s best to always add a fuel stabilizer to your jet ski’s fuel tank if you don’t plan on using up all the fuel in one day or a few days. Another common fuel issue is water in the gas tank from rain or a faulty gas cap, which damages the fuel quality.

We hope our guide and troubleshooting solutions help you get your jet ski back up and running and on the water! Routine maintenance for your jet ski, including charging the battery, inspecting the spark plugs, and adding fuel stabilizer, can help you avoid these common problems in the future.

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