How Does a Jet Ski Speedometer Work? Is It Accurate?

Although riding a jet ski gives you a lot of freedom, the agreed-upon speed limit by the Coast Guard is 65 miles per hour. To determine if you’re at the right speed, you’d check your jet ski’s speedometer. You’ve heard mixed things about using the speedometer, such as how it’s not always accurate. Is that true? How does the speedometer operate, anyway?

Jet ski speedometers work like this: cables connect to the speedometer, and the cables turn, moving an internal magnet within the speedometer cup. The cup indicates your jet ski speed, but this is unfortunately rarely accurate, sometimes being off by 20, even 30 miles per hour!

Wait, that’s a huge discrepancy between your actual speed and the gauged speed. Why are jet ski speedometers so inaccurate? Is there anything you can do to get a truer reading so you can stay within the speed limit? We’ll discuss all that and more in this post, so make sure you keep reading!

How Does a Jet Ski Speedometer Work?

Like any vehicle, your jet ski has a speedometer. This is often built into the dashboard but may be a separate (and more easily removable) device. As you accelerate on your jet ski, the speedometer moves as well, displaying what’s supposed to be your speed on its gauge.

What’s happening behind the speedometer’s outer face that allows it to determine your speed? Well, how a jet ski speedometer works can vary from model to model, but here is a basic rundown of how the speedometer should operate.

Coming out of your jet ski’s speedometer are a series of cables known as drive cables. These are flexible enough to move, as they have to turn often. When your jet ski is at rest, the drive cables should be too. To show your speed reading, the cables will begin turning as you gain speed. Not just one section of the cable moves, but the other side as well.

The motion of the cable nearest to the speedometer’s magnet activates this component. The magnet is part of the speedometer cup, also known as a speedcup. The speedcup features the speedometer’s needle, which moves up or down as you gain and lose speed. 

The magnet rotates around the speedcup, and as it does, it generates its own magnetic field. Now the speedcup has electrical currents coursing throughout it. The speedcup’s torque increases, forcing the cup towards the direction of the magnetic field. As the magnet moves faster, the magnetic field strength increases, pushing that speedometer needle up and up.

The last part of a jet ski speedometer is a hairspring. This small component can outstand the speedcup’s force to retain the needle positioning when your jet ski is not in motion. In other words, the hairspring keeps the needle right at zero. 

Are Jet Ski Speedometer Readings Accurate?

The parts of a jet ski speedometer are not all that different from what you’d see in a car or truck. Yet you know that when you get into your vehicle and see the speedometer’s needle moving that you can trust that you’re actually going at that speed.

Among jet ski owners, a disturbing trend has emerged. Their speedometer readings are often inaccurate, and not just by a matter of 3 miles per hour, but sometimes 30 MPH or more. Here’s a thread on the forum PWC Today with posters lamenting that very fact. 

Most jet skiers find that their speedometer goes majorly over what their actual speed is, but some riders have noted that the speedometer lags behind. The latter is an even scarier situation!

This might seem like a strange phenomenon to you. Jet skis are manufactured to be the pinnacle of performance. The brands that make them include Polaris, Honda, Kawasaki, Sea-Doo, and Yamaha. These are not tiny, unknown companies, nor are they brands unfamiliar with motor vehicles of all kinds.

Surely, no such manufacturer would produce a jet ski or any other vehicle with such a glaring issue as an inaccurate speedometer. This must be a problem with older jet skis only, right? Although that would be nice if it were the case, it isn’t. Jet skis from all manufacturers and of all ages may have inaccurate speedometers.


The speedcup in your jet ski’s speedometer pushes the needle in reaction to the force of a magnetic field, right? Yet what if that’s not the only force that’s applied on the speedcup? What if the speedo wheel behind the ride plate towards the ski’s bottom was creating its own force that causes the speedcup to move the needle way higher than it should?

These aren’t hypotheticals, as that’s exactly what’s happening. The speedo wheel, which sits in water, can be affected by all sorts of things. If the water is a little dingy, that might change how it spins. If your ride plate is open and ventilated, that too can affect the speedo wheel. 

All this results in a speed reading that’s nowhere near indicative of the speed you’re operating your jet ski at.

Is It Such a Big Deal That Your Jet Ski Speedometer Is Inaccurate?

Okay, so your jet ski speedometer’s reading isn’t perfect. Is that really such a huge matter at the end of the day? After all, everything else related to your jet ski works perfectly, it’s just the speedometer that’s a little wonky.

It is indeed a big deal if your speedometer is off. Remember, the Coast Guard has rules in place for jet skiers like yourself. As we said in the intro, the Coast Guard’s speed limit is 65 MPH. If you go over that speed because you can’t trust your speedometer, you can be arrested for speeding in a worst-case scenario. 

Who has the authority to arrest you, you ask? The Coast Guard, for one. Outside of them, law enforcement boats can also pull you over and cuff you. 

You won’t always necessarily get arrested straight away. If this is your first offense or if you’re not going all that fast, you may only be issued a verbal warning. In such a situation, consider yourself very lucky.

The next punishment is receiving a jet ski speeding ticket. Worse than that is a termination of voyage order, where you have to return to land immediately. Law enforcement will also expect you to fix your speedometer before you can head out again. 

What Can You Do to Get More Accurate Numbers from Your Jet Ski Speedometer?

Okay, so it’s for everyone’s safety and your squeaky clean legal record that your jet ski’s speedometer works better than it currently does. What are your options for producing more accurate numbers? 

Buy a New Jet Ski

Well, for one, you can upgrade your jet ski to a new model. Fresh factory-produced jet skis with brand-new components will work the best, including the speedometer. However, going this route leads to the inevitability that your speedometer will fail again as you use your jet ski more and more, so you’re in this endless loop of buying new jet skis. That’s no fun financially. 

Use a Jet Ski GPS App

You can also work with what you have, gauging your speed on a GPS app designed to more accurately produce speed records. Also known as an odometer app, a GPS speedometer app is said to have an accuracy rating of about 99 percent, but that of course depends on the app you download. 

Many such apps can work if you’re offline, and they’re intended for tracking your speed when doing other activities too, such as flying in a plane, bicycling, riding a train or bus, running, walking, and even driving.

Here are some GPS speedometer apps that come highly recommended by jet skiers.

  1. DigiHUD

The first app is DigiHUD, which is available on the Google Play Store. This free app works regardless of if you have a cell connection, which can be spotty when out in the water on your jet ski.

The HUD in DigiHUD stands for head-up display, showcasing information like your distance traveled and your current speed. The normal viewing mode is the default, but you can also switch to HUD mode. This mode acts as a mirrored display of your speed, sort of like a windshield reflection. DigiHUD recommends using this mode if you jet ski after dark.

Here is a rundown of all the data DigiHUD can show you on your virtual speedometer:

  • Battery level indicator
  • Time
  • Odometer
  • Stats
  • Compass
  • Distance traveled
  • Top speed
  • Average speed
  • Current speed

Toggle between speed displays in knots, kilometers per hour (KMH), or MPH. 

  1. Dynomaster

Dynomaster is made for drag racers, but jet skiers use it all the time, especially considering this app is free. Relying on Bluetooth GPS, Dynomaster lets you customize your speedometer so it displays only the information that’s most relevant to you at the time. 

With Dyno Graphs, you can go back and review your numbers for the duration of your trip. Dynomaster is even compatible with Microsoft Excel for exporting data as well as Google Earth. 

  1. SpeedView

The final GPS speedometer app for your consideration is SpeedView, which is only available for Android users on the Google Play Store. Calling itself an “advanced speedometer application,” SpeedView takes the data from your Android’s GPS to create a speed graph as you jet ski. The graph provides such data as how long you’ve been traveling, your distance, direction, and average speed.

An included linear compass will keep you on the right track every time you go on a jet ski ride. If you accumulate riding data you want to hold onto, SpeedView exports it to programs such as Google Earth and more. 

Visit our Boating/Personal Watercraft Page for More Great Content!

Final Thoughts 

Jet ski speedometers have a lot in common with the speedometer you use in your car every day. There’s just one key difference: the jet ski’s speedo wheel leads to a lot of speed reading inaccuracies. Rather than risk getting ticketed or even arrested for speeding infractions, you’re much better off using a GPS speedometer app instead. 

Geoff Southworth

I am a California native and I enjoy all the outdoors has to offer. My latest adventures have been taking the family camping, hiking and surfing.

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