Jet Ski won’t go fast? Here’s what you need to know

Most of the time owning a jet ski is all fun and playing. Sometimes though, you may start to experience problems, one of these common problems is if your jet ski will rev as normal, but will not go above a certain speed, or at all. There are some simple steps to troubleshoot, so follow along below.

As you can see in the image above, there is a broken intake grate as well as lack of sealing between the hull and the pump items. Both of these items need taken care of to provide the best riding experience.

What to do if your jet ski revs but won’t go?

If your jet ski revs but won’t go, the first culprit most likely is something was sucked up in the impeller. This typically is some seaweed, rope, or other item. Take the ski out of the water and do an inspection. The second most likely item would be the wear ring is bad. These should only allow a dime to fit between the wear ring and impeller.

Troubleshooting your Jet Ski Revving but not going:

Something Stuck in the Pump

Symptoms of Something Caught in the Pump

  • Slow
  • Lack of acceleration
  • Vibration
  • Sluggish

There is a good chance that something is stuck in the pump of your wave runner. If you have been traveling in shallow water, or even picked up some surface weeds, you may need to check. Typically you will know it is weeds from the ski vibrating while at higher revs and feeling like you are losing traction. The engine should rev like normal and feel great.

To check out your pump, first either use a dive mask if still in the water, tip it on shore, or pull it out of the water and look under the trailer. You will need to look directly down the pump nozzle as well as under the ski in the intake grate and driveshaft. Make sure these are fully clear from weeds, rope, or anything you could have sucked up.

If you found something, cut it out or use pliers to pull it and you can get back to riding to see if it fixed your problem. If you did not find anything in your pump, keep reading.

Wear Ring

The wear ring is another likely culprit that could cause sluggish acceleration, lack of top speeds, or that feeling of loosing traction.

To inspect your wear ring, you will have to pull your ski out of the water. Wear ring damage can be caused by sucking up sand or rocks causing scaring on the plastic or metal ring, or even from wear over the time of owning and riding your jet ski.

Once you pull your ski out of the water, depending on the size of your intake grate, use a feeler gauge to check the gap between your impeller and your wear ring. Your owners manual should give you the factory clearances, but typically, if you can fit a dime in there it is too much.

Replacing a wear ring is usually straight forward, but it does involve removing the pump to do the work. This can be a few hour job depending on your tools and skill.

Another item that could involve the wear ring is something got stuck. In the Sea-Doo models, they have plastic wear rings. A piece of gravel could get stuck causing a lack of seal and you could have lower performance. This may not be fixed by simply removing the rock but a big chunk can be missing and you need to replace.

Wear rings can become old, brittle and fail. Your wear ring can be spinning when the motor spins. Wear rings are designed to be tight in the pump, but due to age and damage, they can spin with the impeller causing lack of performance.

Driveshaft Spline

It is rare, but your driveshaft impeller spline could have sheared off. This will keep your motor spinning, but you will not be putting power to the water as the impeller wont spin.

To identify this problem, you most likely will have a jet ski that doesn’t move at all in the water. You will be able to rotate the impeller by hand without the engine cranking, or vise versa and moving the driveshaft but the impeller not moving.

Check your Water Outlet

Some skis have a rev limiter due to overheating. Check to see if water is coming out of your jet ski outlet to make sure it is cooling properly. Some waverunners will overheat due to no water coming out and the computer will cause the engine to have a rev limiter to prevent damage. This rev limiter can be causing your lack of power and speed.

If you do not have water coming out of your outlet, you will need to troubleshoot your water lines to see if there is any clogging. Wood, seaweed, rocks, or other small items can get sucked in and cause a blockage.

Check Intake Grate and Ride Plate Gap

On rare occasions, the intake grate or ride plate cause air to be passed through the pump causing cavitation. This can be solved by resealing both the intake grate and the ride plate. This should be done anytime you remove either item.

If your ski does not have a sealed ride plate or intake grate, consult your factory manual and seal them if need be.

Clogged Carberator

If you have a 2 stroke, and your motor is revving but not like it should and it feels like power is getting to the impeller with no cavitation, than it could be a clogged carburetor causing your sluggish issues.

Bad Gas

Bad gas can also be a culprit of a slow speed. Mix some bad gas with deteriorating fuel lines, and you will have a ski that will underperform. Fuel has a short shelf life, so if you let your ski sit for months at a time without using fuel stabilizer, you may need to replace your fuel as well as lines.

Too low of Octane Gas

We found this out on our Honda F12X. The dealer told us we can use regular, but the manual calls for premium. When using regular, there is a noticeable difference of performance of the turbo due to lack of octane feeding the engine. Fill it up with a higher octane premium gas and it is good as new.

Rev Limiter

Some skis may have a rev limiter due to lack of octane in the gas, a learning code, kids mode, or even if there is a supercharger or turbo problem. Check to see if it is limiting your revs at a certain limit. On our Honda ski, the training mode limits revs at 3500 rpm which is just enough to barely get on plane and it just sits there and goes up and down up and down. I am not sure how good this is for the motor by having kids mode bounce off of the rev limiter like this.

Taking on water

This one is a long shot as it is obvious, but check to see if you have taken on some water on your ride or while your ski was sitting. Water weighs 8 pounds per gallon and if you have 20 or so gallons or even half your ski full of water, this will cause a huge performance decrease. It doesn’t take much time to pop your seat or engine cover and inspect.

Bent Impeller

If you sucked something into the impeller such as a rock and bent the impeller, you visually would not see anything stuck in there such as seaweed, or something wrong with your wear ring.

You could have a bent impeller depending on the size of the item of what you sucked in. You will want to check the edges to make sure they are straight and sharp like factory. If there are gouges and bends, I would suggest you get your impeller repaired or replaced.