Jet Ski Cavitation: What Causes It & How To Fix

If you ever ridden a PWC, and it feels like it won’t catch, slipping gears, or simply doesn’t want to go, then you’re experiencing cavitation.

A jet ski that is cavitating will be obvious and annoying. There are several things that will cause cavitation in your jet ski.

Let’s go over why your jet ski is cavitating and what you can do to fix it.

Cavitation Explained

Cavitation can affect any boat with an impeller or prop and is within itself an amazing thing to learn about.

The name comes from cavities forming (bubbles), when the water is reduced below its vapor pressure. The faster the impeller moves, the more cavities are formed which implode under the pressure. They don’t EXPLODE, they IMPLODE, which makes this so amazing and interesting.

These implosions are so powerful that they eat away at the impeller of a jet ski, which makes things even worse. The impeller can become unbalanced and cause more bubbles to form, causing more cavitation.

Cavitation is all around us, not just in PWCs or boats, this video below does an amazing job of covering cavitation:

How To Tell If You’re Cavitating?

A jet ski that is shaking, won’t take off, or has a lack of power is a sign it is cavitating.

Often, people report their jet ski is “slipping gears” or just won’t catch. You give it full throttle, and it has all the power in the world, but just won’t take off.

Reasons For Cavitating

Here is the list of things that will cause a ski to cavitate:

1. Damaged impeller
2. Damaged wear ring
3. Damaged driveshaft
4. Damaged through-hull seal.
5. Damaged intake-grate
6. General damaged to the jet pump

What is most likely to cause the damage above is sucking something up. Rocks and sticks are the most likely culprit of a jet ski cavitating, but even things like ropes, sand, to the more crazy things like snakes, I’ve seen cause them to cavitate. Yes, I had a guy once suck up a snake, it did just enough damage to make the ski act funny.

Then you have manufacturer defects or simply parts wearing out. A worn out driveshaft or one that was bent due to sucking something up can cause the impeller to wobble, which makes them unbalance and will cause cavitation.

99% of the time, you’re cavitating because you sucked something up. Even if you think you didn’t, it’s almost always due to sucking something up.

How To Fix Cavitation

Since the most common reason for a jet ski to cavitate is because something was sucked up into it, you will need to remove the item that was sucked up and repair the damage.

Here is what you need to do first:

1. Get the ski out of the water and on a trailer or stand.
2. Secure the trailer so it doesn’t move.
3. Look under the ski into the intake grate to see if you can see anything out of the ordinary.
4. Look at the rear of the ski into the pump to see if you can see anything.
5. Remove the jet pump from the jet ski to fully see if any debris is hiding or stuck – best to let the repair shop do this. A lot of the debris won’t be easy to spot unless the jet pump is removed.

You need to see what is stuck in the impeller and what damage was done. If the wear ring or impeller are damaged, the jet pump must be removed and those items fixed. It’s best to let the local repair shop do it for you as you need a special impeller removal tool and wear rings on some models can be tricky.

Note: You CAN NOT get to the jet pump from the inside of your jet ski, the pump is on the outside. I’ve had several people start to tear their engine apart to get the pump, and it only makes things worse for themselves.

Sometimes it can be an easy fix of simply knocking the rocks loose, as it may have not done enough damage to cause constant issues.

Other times, the rock does a lot of damage and the impeller and/or wear ring needs to be replaced. If you see cuts and, in general, a non-smooth impeller, it needs to be replaced. Even slight barbs and cuts will cause a jet ski to cavitate.

It is possible to take out the jet pump and notice nothing be stuck in it, but damage was still done. Often, it only damages the wear ring, which is what it is designed to do. PWCs are powerful, so the item that was once stuck is now blown out, but the damage has been done and it now cavitates.

Is Cavitation A Maintenance Routine?

An impeller is always experiencing some kind of cavitation, but the manufacturer designs it so that it’s so small it’s not an issue.

The only time cavitation can become an issue is if you suck something up or the jet pump is damaged.

There are the few times something in the pump or connected to the pump fails and causes cavitation, but most often it’s because of someone sucking something up.

Costs To Fix

The cost to fix a jet ski that cavitates will depend on what is damaged.

It’s all over the place, sometimes it’s a stick that is stuck in the impeller, but it didn’t do any damage, so it’s only a labor charge. Sometimes it’s a lot of rocks and the impeller and wear ring need to be replaced.

To give you an idea, it can cost as little as $100 to $1,000, if not more, especially if you damage the jet pump housing, to replace the impeller and wear ring by a repair shop. The price greatly depends on what is damaged and what type of jet ski you have.

You can save money and do it yourself, for example the Sea-Doo Spark without iBR is super easy to replace the wear ring and with the right impeller removal tool you can swap the impeller. Some jet skis are a pain to replace the wear ring, but it’s not the hardest thing in the world. Just make sure to tighten everything back to the correct specs, as some jet skis will sink if you don’t tighten and align things up right.

Not Covered Under Warranty

Unless the cavitation was due to a manufacturer defect, then it won’t be covered under warranty.

The cavitation that most experience is often done by someone sucking something up, so it’s NOT a warranty item.

You need to be careful while operating in shallow water, as covered in this post.