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What Causes Jet Ski Cavitation And How To Fix + Avoid It

Have you noticed your jet ski feeling a bit shaky when you try to take off? Or it feels like it wants to go, but doesn’t?

Well, that could be due to a common issue known as cavitation. I notice that sometimes, people mistake it for “slipping gears.”

Let me explain what cavitation is and why it might be causing these problems for your jet ski below.

What Is Cavitation, And How Does It Affect Jet Skis?

Cavitation effects boats with impellers or props and is fascinating.

It occurs when water pressure drops below vapor pressure, forming bubbles that implode, not explode.

These implosions erode the impeller, which makes the cavitation get worse.

Cavitation is everywhere, not limited to boats. Watch this video below to learn more:

How Do You Know Your Jet Ski Is Cavitating?

You’ll know your jet ski is having cavitation issues when you give it gas, and it doesn’t want to go. Many people mistake it for “slipping gears” or a slow take-off. The jet ski make eventually catch, and you can reach top speed, but it takes forever as it feels like the jet ski is “spinning its wheel’s”.

What Causes Jet Ski Cavitation?

Cavitation damage is often caused by sucking up debris like rocks, sticks, ropes, and even unusual items like snakes. (Yes, it’s happened to me.)

It can also be from manufacturer defects or worn-out parts like a bent driveshaft, leading to impeller imbalance.

In most cases, I see, cavitation is due to sucking something up and damaging the wear ring and impeller.

Comparing two Sea-Doo impellers one is damaged the other is good

How To Fix A Jet Ski that Cavitates

Since the most common reason for cavitation is because something was sucked up, you will need to remove the item that was sucked up and repair the damage.

Steps:

  1. Get the jet ski out of the water and on a trailer or stand.
  2. Secure it so it doesn’t move and have the engine off.
  3. Look into the intake grate to see if you can see anything out of the ordinary.
  4. Look at the rear into the pump to see if you can see anything.
  5. Remove the jet pump 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.
Sea-Doo pump front showing good impeller and good yellow wear ring looking between intake grates

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 machine, the pump is on the outside!!! I've had several people start to rip their engine apart to get to the pump, and it only makes things worse for themselves. 

The Easy Fixes

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

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 it to cavitate.

But There Is Nothing In Pump?!

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. Jet skis are powerful, so the item that was once stuck is now blown out, but the damage has been done and it cavitates.

Is This a Routine Maintenance Item?

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 it can become an issue is if you suck something up or the jet pump is damaged.

There are the few times something in the jet pump or connected to the jet pump fails and starts cavitating, but from my years in the field, the most often it’s because of someone sucking something up.

What The Costs To Fix?

Showing damaged impeller cone next to a good one.

The repair cost varies based on the damage.

It can range from $100 to $1,000 or more, depending on what needs fixing and the type of machine you have.

DIY is an option, especially for models like the Sea-Doo Spark without iBR, which is straightforward. Some models may be harder but manageable.

Proper tightening and alignment are crucial to prevent issues. Some PWCs can sink if the proper bolt is not tightened in the jet pump area.

It’s Not Covered Under Warranty

Unless it was due to a manufacturer defect, then it won’t be covered under warranty. Let me be blunt, it’s most often not a manufacturer defect, so don’t expect warranty to help.

The cavitation that most PWCs 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.

Author

Steven

I started working at a power sports dealership in 2007, I worked in parts, service counter, and as a technician before moving to sales in 2013. I created StevenInSales.com in 2014 to answer common watercraft questions I would get from people. Now managing the site full-time, I continue to provide advice and web tools for my readers about watercraft. I've owned several watercraft, with a Sea-Doo Spark as my current main PWC.

Comments

  1. Hey Steve. Have a 2016 3up Spark purchased used in 2022. It has gone through 3 wear rings in under 20 hours of use all in the Parry Sound area of Georgian Bay which I think is fairly “clean” water. The first time was in a very weedy bay but the other 2 were while cruising open water. Is this common for the Spark model ? Seems to blow a hole in the side of the wear ring almost too easily. Getting frustrated with this so very seriously considering the stainless ring. Thanks for any advice.

    Reply
    • This is not normal, and I would check the pump and bearings to make sure there is not too much wobble or something else is causing it to fail that quickly. If you can’t find anything, then moving to the stainless steel will be the next best option.

      Reply

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