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10 Reasons Why Your Jet Ski Won’t Start or Accelerate [Video]

10 Reasons Why Your Jet Ski Won’t Start or Accelerate [Video]

It’s safe to say that the 10 most common reasons why a jet ski won’t start or accelerate are as follows:

  1. Dead battery
  2. Starter relay issues
  3. Defective spark plugs
  4. Wrong fuel
  5. Wrong modes or keys
  6. Clogged pump
  7. Water in the gas
  8. Engine and fuel line issues
  9. Supercharger malfunctions
  10. Other possible issues
If you want to dig into the details, keep reading.

We at JetDrift have compiled all you need to know under one roof!

10 Reasons Why Your Jet Ski Won’t Start

You’ve just launched it, but now your jet ski won’t start?

This can be especially frustrating if others are waiting behind you on the ramp. This is why it’s always a good idea to start your jet ski while it’s still on the trailer, or even better to try starting it at home in the garage.

You can turn the engine on and let it run for 15 seconds without cooling. This won’t damage the engine or other parts at all as long as you keep the RPM low!

Also, never overlook the pre-ride checklist, as accumulated gas vapors in the engine compartment could result in an explosion.

The other problem that commonly occurs when starting the engine is that it won’t accelerate as it should. It may mean more work, but if this happens it must be looked into immediately.

When trying to troubleshoot a jet ski that isn’t starting, you can break the problem down into a few basic possibilities.

If the jet ski won’t start or run at all, the ignition is the first thing you’ll want to look at.

The problem could be with the fuel system or perhaps the carburetion, which can happen if you haven’t used your jet ski in a while. But before anything else, check the battery!

Let’s get down to the nitty-gritty and talk about these issues in detail!

1. Dead Battery

A dead battery is the most common reason for a jet ski not starting.

Even if you have a new battery or you’re sure the battery is charged, a dead battery is the most common problem that occurs at the start of every summer season. This is why we tell everyone that a proper winterizing process is vital.So, if your jet ski won’t start, before doing anything else immediately check the charge on your battery.

  • If you turn the key and nothing happens, then it’s very likely the battery is totally shot and will have to be replaced. But to be sure, check it with a charger.
  • If you turn the key and the display goes on, but when pressing the start button all you ger are clicking sounds, the battery is weak. This means it needs recharging.
To give your battery a good charge, use a smart battery charger, one that won’t exceed 2 amps. Let the battery recharge overnight if possible so that it will be fully charged. If you don’t have time, you need to at least recharge it for several hours.

Helpful Tip: To prevent the battery from dying on you all the time, get a solar panel. When your jet ski is not being used, use the solar panel to recharge the battery!

2. Starter Relay Problems

Just like cars and motorcycles, a starter is what starts your jet ski engine, and like anything else it can have issues.

The starter relay is what transmits power to the starter motor from the battery so it can turn on the engine. To figure out whether it’s the starter relay that’s causing the problem or the battery is by the number of clicks.

If the battery is bad the starter relay will quickly make multiple clicks, but if the relay is bad you will only get one click when pressing the start button.

So, if you try starting your jet ski and all you hear is one solid click, it’s very likely that you have a bad starter relay. You can also tell if the starter relay is bad if you are forced to press the start button several times to get the jet ski to start.

You can very likely get your starter relay replaced at your local dealer. They usually have them in stock. Or, you can buy one online and if you know what you’re doing and have the proper tools, you can replace the starter relay yourself.

However, you need to know that for some models, the starter relay could be more complicated to install. It may only be a couple of wires but getting to the relay can be quite difficult. Read your owner’s manual before doing anything!

If you don’t know how or just don’t want to replace the starter relay yourself, just take your jet ski to the dealer or a reputable service shop.

3. Spark Plugs 

Spark plugs are often the problem if your jet ski engine turns over, but doesn’t start, especially if you have a 2-stroke jet ski.

Take the spark plugs out and examine them to see whether they’re wet or dry. If they’re dry and light brown in color, you have the correct fueling. If you find one wet plug, that carb may have a problem, or the problem may be the ignition on that cylinder.

It’s always wise to keep an extra set of spark plugs on hand, especially when you own a 2-stroke jet ski!

When replacing spark plugs, experts recommend that you put a tiny amount of gas or starter fluid into the spark plug holes to give them an extra boost.

4. Wrong Fuel

If your jet ski won’t start or accelerate the problem may be fuel quality, especially if it’s been a while since you last used your jet ski.

If you rarely use your craft, you should add some fuel stabilizer to your tank each time you fill it up.

Doing this will keep your fuel fresh, which helps your jet ski to start quickly after being stored. Fuel stabilizers remove water, which prevents corrosion and cleans fuel injectors and carburetors.

Furthermore, it would be smart to keep a bottle of fuel stabilizer at home because you will need it when it comes time to winterize your craft.

Water in the gas could also be an issue. People most commonly get water in their gas from rain or because of a loosed fuel gas cap. Check the gas in your tank and in the fuel line as well!

5. Other Possible Issues

Above we discussed the most common reasons for a jet ski not starting.

Aside from these, there could be numerous causes. So, in most cases it would be best to take your jet ski to the dealer for an inspection.

New jet ski models come with very informative gauges and screens that show error codes when something malfunctions. If there is an error code showing on the screen, just check your owner’s manual to find out what that code refers to.

Before transporting your jet ski to the dealer, make sure to check everything you can:

  1. If you see an error code, find out what it refers to in your owner’s manual.
  2. Check and recharge your battery or replace it if necessary.
  3. Check and replace your starter relay if necessary.
  4. Replace the sparkplugs if necessary.
Check for water in your fuel tank and fuel line as well.

If Your Jet Ski Won’t Accelerate

Another very common problem is when your jet ski won’t accelerate, which is when your jet ski won’t take off or does so very slowly. But if it does take off you can’t reach top speed for some reason.

You can also feel your engine vibrating, or it may just shut off during your ride.

If any of the above occurs you need to have the problem investigated immediately. These types of problems can be caused by various issues. Here are the most common:

6. Wrong Modes or Keys

If your ski seems sluggish and is just going too slow, the cause may be that you’re in the wrong mode or you could be using the wrong key. Jet skis oftentimes have different riding modes, and some have a learning key.

Before hitting the water, check to see if you’re holding a “Learning Key” or “L-Key” because those will limit take off as well as speed. Some jet skis have a built-in learning mode and when it is in that mode a light will turn on that says “SLO Mode,” “L-Mode,” or something like this.

If you’ve got the right key, then the lack of acceleration could be due to the driving mode.

With so many jet skis getting faster and faster many manufacturers have installed different driving modes. Typically, the default mode would be a “Touring Mode,” which gives you a smooth but enjoyable ride. There is also an ECO Mode, which also gives you a slow takeoff and limits your top speed. But you have to activate the ECO Mode by pressing the button. For full power and acceleration, find the Sport Mode button.

If you’re not using a learning key, and you’re not in the wrong mode, the problem might still be with the key. If this is a new or used jet ski that you just brought home from the dealership, the keys could be programmed wrong. Try the other key because they could have got them backwards.

7. Sucked Something Up

What also commonly happens with jet skis is that they suck things up and this can certainly keep it from taking off.

Most of the time you don’t even know that this happened because the engine is so powerful that it blows whatever it is right out of the pump.

But at other times you’ll hear a strange sound, or your jet ski will violently shake and then you’ll know that something got sucked up. If you’re trying to accelerate and your jet ski is shaking or lacks power, then odds are that something got sucked up.

When this happens, it can damage the impeller, wear ring, or sometimes the drive shaft.

Things that get sucked up and can cause these types of damages are small rocks, ropes, debris, and anything else that may be in the water.

The problem could also be that you have a tow rope, or some seaweed wrapped around the drive shaft and this keeps it from spinning properly or may be impeding the flow of water.

Even though there is an intake grate in front of the pump, it simply can’t filter out everything. To learn more about these problems and learn how to remove these objects we recommend this tutorial.

Unfortunately, many of the issues discussed above will require the help of a dealer or repair shop.

Anything having to do with the pump should be taken care of on dry land by a skilled professional, especially if you have break system on your jet ski as those make it more difficult to reach the pump.

8. Water in the Gas

This is something we discussed above, the problem of having water in your gas.

Water can even get into your gasoline at the gas station, but people more commonly get water in their gas from rain. They may not be replacing the gas cap tightly enough or the gas jugs they use get water in them.

Another problem with gas is that it actually expires and that means it goes bad. This happens more quickly than you probably think too. To avoid this, you need to put fuel stabilizer in the gas tank before storing your jet ski for a few months. If you don’t then it’s unlikely that your gas will be good when you try starting your jet ski after a month or two. And when you put the fuel stabilizer in make sure it’s mixed through the entire system.

You need to know which kind of gas to use as well. If you own a high-performance supercharged jet ski, then you have to be more careful. Read your owner’s manual for the manufacturer’s recommendation when it comes to the type of gas to use.

9. Engine & Fuel Line

Aside from everything else we’ve discussed, there are a number of other engine issues that may cause problems during your ride.

If you have a 2-stroke jet ski, you could have a clogged carburetor. This commonly happens if the jet ski has been sitting for a couple of months without a fuel stabilizer.

If the carburetor is clogged it won’t start at all, won’t want to run, or just struggle to run. Take your pick.

You could also be having problems with your fuel line. It’s always important to check your tank as well as your fuel line very carefully for dripping gas as this could cause the engine to explode in a worse case scenario!

If you’re having engine trouble, a reputable professional should take a look at it right away.

10. Supercharger Malfunctions

If your jet ski starts okay and takes off without a problem but there is no way you can get it to go as fast as it usually does, then you could have a bad supercharger.

If this is what’s happening and your jet ski is just doing fewer RPMs, our recommendation would be for you to stop riding until you’ve taken it to a professional who can work on the problem. It is no easy task to repair a supercharger!

If your supercharger is blown, then metal pieces could be in your engine and be doing a lot of damage. A reputable professional will know how to deal with these issues.

Did you know that in many cases the supercharger needs to be rebuilt after every 100 hours of use or after 2 years, whichever comes first? It’s true that prevention is better than the cure, so it would be wise to get your supercharger rebuilt during the recommended period!

* WARNING! If you do not have the proper knowledge, training, experience and tools to handle the repairs above, we highly recommend that you transport your jet ski to a local dealership or a reputable service/repair shop.