Jet Ski Speedometers: How Accurate Are They? [Video]
As a rule of thumb, the most common types of jet ski speedometers are as follows:
- Paddle wheel speedometer
- RPM-based speedometer
- GPS-based speedometer
If you want to find out more about these units and their accuracy, you’ve come to the right place.
Let’s get down to the nitty-gritty and talk about each in detail!
Which Type of Speedometers do Jet Skis Have?
Paddle Wheel Jet Ski Speedometer
Most vintage jet skis were designed with simple paddle wheel speedometers. As the name suggests, the heart of this assembly was a small paddle wheel usually planted into the ride plate.
How does it work?
When the ski moves the passing water continuously turns this paddle wheel, sending signals to an electrical speed sensor.
This sensor is attached to the gauge or the ECU of the ski, which converts the signals into digits that can be read on the display.
In other words, on these skis, the speed is measured by how fast the water spins the paddle wheel.
The biggest complaint against this design is that it is largely inaccurate.
Let’s face it, the paddle wheel rarely runs in clean water, since the flow under the jet ski hull is anything but steady.
If the ride plate suffers from issues like ventilation, the paddle wheel is often just spinning in the bubbles rather than running at the correct speed.
Also, when the machine turns, jumps, or slides the paddle wheel is also prone to delivering incorrect signals.
Consequently, a paddle wheel speedo often gives a false indication of the actual speed of the jet ski.
On top of that, the wheel is prone to getting clogged by debris, breaking, or accidentally falling off.
RPM-Based Jet Ski Speedometer
RPM-based jet ski speedometers became more prevalent with the advent of modern LCD displays.
Unlike their base predecessors, these modern gauges show several types of useful information including engine RPM.
To get rid of unreliable paddle wheels, some manufacturers decided to switch to RPM-based speedometers. These systems are designed to estimate the speed of the vehicle based on the revolutions (RPM) of the engine.
They also take duration into account, which makes sense; the longer you keep the throttle depressed at a given RPM, the faster the jet ski will go.
Therefore, these systems lack any paddle wheels, sensors, or GPS units.
They can be more accurate than outdated paddle wheel sensors, but can never be as precise as a GPS-based jet ski speedometer.
GPS-Based Jet Ski Speedometer
If you are looking for a more accurate jet ski speedometer, a GPS-based unit is the only way to go.
The onboard GPS unit on a jet ski is typically built into the LCD display and calculates the speed based on information from several satellites.
GPS-based jet ski speedometers appeared around the Millennium when manufacturers started to limit the top speed of their fastest models to 67 mph, due to an agreement with the United States Coast Guard (USCG).
Since then, high-performance jet skis are typically designed with a GPS-based speedometer, which electrically limits their top speed.
Are Jet Ski Speedometers Accurate?
Believe it or not, no jet ski has a perfectly accurate speedometer. As a rule of thumb, each jet ski speedometer tends to show higher numbers than the actual speed, which is why they are often called “dreamometers.”
You can expect the least accurate result on a paddle-wheel speedo, while their RPM-based counterparts are slightly more precise.
The most accurate jet ski speedometers are arguably GPS-based units, but they are also prone to displaying about 0.5-3 mph more than the actual speed.
Depending on the age and model, jet skis feature very different speedometer designs.
For many years these tiny vessels were designed with paddle-wheel speedometers, which were very inaccurate and prone to clogging or breaking.
More advanced jet skis with LCD displays often utilized RPM-based speedometers, which estimated the speed based on the engine RPM and throttle handling.
The most advanced jet ski speedometers feature a built-in GPS module that calculates the speed like any regular GPS-based speedo.
Unfortunately, even these units are not entirely accurate, since they often show 0.5-3 mph over the actual speed.
The accuracy of a jet ski speedo depends on many factors like the make, model, and design of the speedometer.
If you want to measure the actual speed of a jet ski, you will need radar or a high-accuracy handheld GPS!
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