The most common reasons why a jet ski won’t start are as follows:
- Shut-off chord (lanyard) is not attached
- Lock mode is active
- Wrong key
- Low battery
- Starter relay issues
- Bad starter motor
- Defective spark plugs
- Faulty lever
- Bad fuel/or no fuel
- Fuel line issues
- Oil line issues
- Clogged air filter
- Jet pump issues
- Burnt fuse
- Broken start button
- Faulty sensors
- Other electric or computer issues
- Engine overheating
- Engine is hydro-locked
- Major engine problems
If you want to learn more about these issues and the remedies, keep reading!
If your jet ski starts but doesn’t accelerate or bogs down, you may want to check for those remedies in this post!
20 Reasons Why a Jet Ski Won’t Start
1. Shut-Off Chord is Not Attached
One of the most common reasons why so many jet ski won’t start is arguably an improperly attached shut-off chord (safety lanyard).
Make sure you’ve attached the clip to the shut-off switch on the handlebar.
2. Lock Mode is Active
Some jet skis feature a “Lock mode” to prevent unauthorized use. As its name implies, while this mode is active, the jet ski won’t start!
Select “Unlock mode” using the remote-control transmitter, which is a typical accessory on newer Yamaha jet skis. Be careful, because with the same transmitter you can often select the “Low RPM mode,” meaning that engine power will be limited.
Make sure that you start the engine in “Normal mode.” To make this process easier, the different modes are indicated by different beeping sounds.
3. Wrong Key
While Yamahas come with a remote transmitter, Sea-Doos feature a special D.E.S.S. key. If you have a Sea-Doo, make sure to start the jet ski with the right key.
If it won’t start, try reattaching it. In many cases this simple trick solves the issues.
The worst-case scenario is when the key is broken, and you have to take the craft to a dealer. Fortunately, this is rare.
4. Battery Issues
If you try to start your jet ski but nothing happens, it is likely a battery problem. In many cases the battery has discharged, or its connections have loosened or are corroded.
Inspect the battery and charge it if necessary. Best practice is to leave it on the charger overnight. You may also want to check the cables and connections.
It’s safe to say that the main reason why jet skis won’t start is battery issues.
If your battery is still weak after you’ve recharged it, this is a clue that it has to be replaced.
Be very careful with battery cables, as mixing them up can damage the jet ski’s electric system!
5. Starter Relay Issues
If you start the jet ski but you only hear one click, this probably means the starter relay is broken. Also, if you typically have to press the start button several times to fire up the engine, this is also a clue that the starter relay is bad.
As replacing this part can be tricky, best practice is to leave it to the professionals.
(A starter relay is also known as a starter solenoid.)
6. Bad Starter Motor
Not only the relay, but the starter motor can go bad as well. Inspect this key part and replace it if needed.
7. Defective/Fouled Spark Plugs
Spark plugs can also cause a lot of headaches, especially on 2-stroke jet skis. Improper carb settings often lead to fouled spark plugs and starting issues.
Remove and inspect the spark plugs and replace them if necessary. If you have a 2-stroke jet ski, it’s recommended that you keep a set of spare spark plugs on you, and the required tools of course.
8. Faulty Levers
It’s a lesser-known fact that the faulty levers can also cause starting problems. Make sure neither the throttle nor the brake lever is squeezed or broken.
9. Bad Fuel/No fuel
If your engine cranks but won’t start, you should check whether there is fuel in your tank. This step seems obvious, but a quick visual check never hurts. (Fuel gauges can also malfunction.)
Also, make sure that the gas is fresh. If your jet ski has sat for a couple of months without a fuel stabilizer in its tank, the gas may be stale. Another common problem is water/dirt in the gas.
If it has gone stale or is contaminated, you must drain the fuel tank and refill it with fresh gas.
10. Fuel Line Issues
Even if the gas is fine, it may not be reaching the cylinders. This is why you have to check the entire fuel line as well.
Fuel pump, hoses, injectors, and carburetors all may become clogged or damaged.
11. Oil Line Issues
Just like the fuel line, the oil line can clog as well. If this happens, the oil pressure drops and a lot of new jet skis won’t start at all. Instead, an error message appears on the screen to warn you of the issue. Another symptom of low oil pressure is overheating.
12. Clogged Air Filter
It seems many systems can get clogged on a jet ski, and the air filter is no exception. In many cases dirt and oil builds up and completely clogs the filter, which prevents the engine from starting.
Check the air filter and clean it if necessary.
13. Jet Pump Issues
Jet skis have direct drive, meaning that the engine spins the impeller immediately after it starts. If the pump has sucked up something like a rope or a small rock, it can completely stop the impeller.
If the impeller is unable to rotate freely, it can block the whole engine. Thus, you may want to inspect the pump to make sure it’s completely clear!
14. Burnt Fuse
Sometimes the source of the starting issue is just a blown fuse. Check the fuse box and replace the blown fuse(s) if you find any.
15. Broken Start Button
Just like any other part, the start button can go wrong. Although it’s not the most common reason for PWC not starting, if you can’t find what is causing the error, it’s recommended that you check the start button as well.
16. Faulty Sensors
New jet skis come with complex systems that feature many sensors. If a sensor goes bad it can foul the main computer and can cause unjustified error codes.
Finding and replacing a broken sensor is always difficult, so best practice is to leave it to a dealership.
17. Other Electric or Computer Issues
Besides the sensors, electrical connections may become loose. What’s more, in the worst cases the jet ski’s computer (known as ECU or ECM) also has problems.
These issues often generate fault codes, which you can read with a diagnostic cable and software.
18. Engine Overheating
Engine overheating is a pretty common problem on jet skis. It can be caused by several issues, from a clogged cooling system to improper lubrication.
If your jet ski engine overheats, the computer may stop it and will not allow it to restart until it cools down.
19. Engine is Hydro-locked
Hydro-locking means water has seeped inside the cylinders, so the engine cannot be started. As this is a serious issue, avoid starting the engine as it may end in serious damage.
Best practice is to take the jet ski to the dealership so they can clean out the water in the cylinders.
Are you wondering how water can get inside the engine? In a nutshell, the most common reasons are as follows:
- A lot of water leaking into the engine compartment
- You’ve towed the jet ski with another vessel at too high a speed
- You’ve flipped the jet ski in the water going in the wrong direction
20. Major Engine Problems
The worst-case scenario is arguably when your jet ski has major engine problems. It could be a seized engine or even a blown supercharger.
Unfortunately, all of these problems may end in costly repairs and a lot of hassle. The good news is that major engine malfunctions are significantly less frequent compared to other malfunctions.
As you can see, there could be many reasons why a jet ski won’t start. In many cases it’s just a drained battery or fouled spark plugs that causes the malfunction.
Fortunately, most of these issues can be easily solved.
But if your jet ski has major engine or electrical problems, it’s highly recommended that you take it to a reputable service shop for an inspection!