A jet ski engine has many similarities to your car and truck engines, but they vary on many things.
One thing that is different in comparison to cars is that a jet ski uses a stator instead of an alternator.
While a stator and alternator work very similarly, they’re not completely the same and have some unique differences. In this post, I want to go over why a stator is used instead of an alternator and the other parts of the charging system.
Jet Skis Use A Stator Instead Of An Alternator
Jet skis do not have an alternator and instead use a stator for their charging system.
A stator works very similar to an alternator, both charge your battery, but a stator is more focused on maintaining the charge (“trickle charge the battery“).
A stator is mostly used on smaller engines like jet skis because they don’t take up as much room, simpler, and they can be stored inside the engine block. I consider this as a huge advantage, especially in such wet and rough environments.
A motorcycle stator and jet ski stator are similar, in fact, some manufacturers repurpose motorcycle engines for watercraft.
Why Do Jet Skis Use A Stator?
There are 3 reasons why a stator is used over an alternator.
- Stators are smaller.
- Stators can be built into the engine, which cuts down on weight and costs of manufacturing.
- Stators are simpler.
A stator is a simplified alternator that produces just enough power for small engines with batteries.
Stator Vs. Alternator
What makes a stator different from an alternator is the magnets.
All generators move copper wires through a magnetic field to create electricity. A stator and alternator are no different and work the same way.
What is different is that a stator uses fixed magnets and an alternator uses electromagnets.
Since the alternator creates its own magnetic fields, its power output is NOT dependent on the engine’s RPMs.
A stator is dependent on the RPMs, and why it’s more of a maintainer than a charger. Due to the irregularity of power, a voltage regulator (also called a voltage rectifier) is used.
Fixed magnets allow stators to be smaller and lighter, and you can put them inside the engine block.
A voltage rectifier, or also called a voltage regulator, takes the power produced by the stator and converts the AC power into DC power and smooths it out to make it more constant and predictable.
Cleans It Up
Since a jet ski uses a stator, the magnets are fixed, they can’t adjust the field, so the faster the engine goes the more electrical power the stator produces. Making too much power could fry sensitive electrical parts or even fry the battery.
Using a voltage regulator cleans up the electrical mess and makes it into something that is useful.
The voltage regulator takes a lot of abuse and will wear out over time.
Signs Of A Bad Voltage Regulator
One sign the voltage regulator has gone bad is that the jet ski will flash a “12-Volt Low” on the display, but this could also mean the battery is bad, grounds are dirty, or a fuse is bad.
Most of the electrical issues I see tend to be a bad battery more often then a bad voltage regulator, but they do wear out.
I consider replacing the voltage regulator as not being hard, it’s often next to the battery and comes off with a few screws and unplugging wires.
Just make sure the battery is disconnected before you replace one.
How To Test Charging System
Testing the charging system to know if the stator or voltage regulator is working fine is similar to any other small engine.
With the jet ski out of the water, here is how you test the charging system.
- Connect a volt meter to battery.
- Turn the engine on and look at the voltage reading.
- Rev the engine to 5k RPMs and look at the voltage reading.
- Turn engine off, don’t run the jet ski out of the water for no more than 30 seconds.
If the voltage reading on both is NOT between 13.5 and 15 volts, then the voltage regulator or stator is bad. If the voltage reading is over 15 volts at 5k RPMs, then the voltage regulator is bad.
Here is a video on how to check the stator: