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What Is Cavitation, And How Does It Affect Your Jet Ski?

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 the jet pump “slipping gears.” I find it interesting, but 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 it get worse. It’s everywhere, not limited to boats. Watch this video below to learn more:

A common Sign:

You’ll know your jet pump is having major 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. You may eventually catch, and the jet ski can reach top speed, but it takes forever as it feels like the jet ski engine is “spinning its wheel’s”.

You’ve Sucked Something Up!

When you suck up debris such as rocks, sticks, ropes, and even unusual items like snakes (yes, it’s happened to me), that creates cavitation in the pump of your jet ski. It can also stem from manufacturer defects or worn-out jet ski parts like a bent driveshaft, causing impeller imbalance. In most cases I’ve seen, it’s due to sucking something up and damaging the jet ski’s wear ring and impeller.

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

The Step-By-Step Solution

Since the most common reason for the damage to your jet ski pump is that something was sucked up, you will need to remove the item that was sucked up and repair the damage.

Steps:

  1. It’s important to get the jet ski out of the water and on a trailer or stand.
  2. Secure the jet ski 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 jet ski 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 inspect what is stuck in the impeller and assess the damage. If the jet ski’s wear ring or impeller are damaged, the jet pump must be removed and these items repaired. It’s advisable to have the local repair shop handle it for you, as you may require a special impeller removal tool, and wear rings on some models can be tricky to work with.

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 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 the jet ski’s impeller and wear ring to cavitate constantly. Other times, rocks can cause significant damage, necessitating the replacement of the impeller and/or wear ring.

If you observe cuts or a generally non-smooth impeller, replacement is necessary. Even “slight barbs” and cuts will cause it.

But There Is Nothing In The 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. It’s important to understand that jet skis are powerful, so the item that was once stuck is now blown out, but the damage to the pump has been done and it cavitates.

Is This a Routine Maintenance Item?

An impeller is always experiencing some kind of cavitation, but the jet ski 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.

$100 to $1,000

Showing damaged impeller cone next to a good one.

The repair cost varies based on the damage, ranging from $100 to $1,000 or more, depending on what needs fixing and your machine’s type. DIY is an option, particularly for models like the Sea-Doo Spark without iBR, which is straightforward. Some jet skis may be more challenging but still manageable. Proper tightening and alignment are crucial to prevent issues. Failure to tighten the proper bolt in the jet pump area correctly can cause some jet skis to sink.

Not Covered Under Warranty

Unless it was a manufacturer defect, it won’t be covered under warranty. Let me be blunt: it’s usually not a manufacturer defect, so don’t expect warranty coverage to help. This may not be what you want to hear but, the cavitation that most jet pumps in jet skis 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.

Sum Up

Cavitation is an interesting thing to experience, not only for boats, but jet skis experience it as well. The most common reason your jet ski’s jet pump will cavitate is due to sucking something or an imbalance with the impeller. Most of the time, replacing the jet ski’s impeller or wear ring will fix the odd take-offs you’re seeing due to cavitation.

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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