Signs of Cavitation In A Jet Ski Plus How To Fix It

If you have ever ridden a jet ski, 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 for your jet ski.

Let’s go over why you’re experiencing cavitation in your jet ski and what steps require a fix to most models.

Cavitation Explained

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

The name cavitation 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 cavitation so amazing and interesting.

These implosions are so powerful that they eat away at the impeller, 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 a jet ski or boats, this video below does an amazing job of covering it:

How To Tell If You’re Experiencing Cavitation?

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

Often, new riders report it’s “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.

Causes of Cavitation Affecting Jet Skis

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

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

Then you experience cavitation from jet ski 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 in a jet ski.

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 In A Jet Ski

Something getting sucked up commonly triggers cavitation, meaning you must take out that piece and correct the destruction.

Here are the fixes you need to do first:

1. Get the jet ski out of the water and on a trailer or stand.
2. Secure the trailer so it doesn’t move.
3. Look under the jet 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 jet pump to fully see how or 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.

For most fixes, you need to see what is stuck in the impeller and what damage was done. If the wear ring or impeller are damaged, the pump must be removed, and those items fixed to solve cavitation in your jet ski. 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: It’s good to know the jet pump cannot be reached from the inside, 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 cavitation 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 jet ski 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 it to cavitate.

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

Cavitation A Maintenance Routine?

Every impeller encounters cavitation; manufacturers refine it to stay negligible, bypassing harm.

The only time cavitation can become an issue is if you suck something up or jet pump becomes 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 jet ski riders sucking something up.

Costs To Fix

The cost to fix cavitation will depend on what is damaged to what is savable.

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 with jet skis it’s a lot of rocks and the impeller and wear ring need to be replaced.

To give you an idea, cavitation damage for a jet ski can cost as little as $100 to $1,000, if not more, especially if you damage the 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 craft 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 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 will sink (ask me how I know) if you don’t tighten and align things up right.

Not Covered Under Warranty

Cavitation from manufacturer defects will be covered under your jet ski warranty; otherwise, it’s not covered.

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

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