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How Jet Skis Keep Their Batteries Charged While Running

Do jet skis have alternators? This may be shocking to some, but jet skis don’t have alternators and instead use a stator. The charging system found in modern jet skis doesn’t need a lot of power to keep things going.

What is a stator, and how is it different from an alternator when it comes to jet skis, let’s find out!

Alternators Vs Stators

A stator works very similar to an alternator, both can charge the battery in a jet ski, but a stator is more focused on maintaining the charge (“trickle charge the battery“).

A stator is mostly contained in smaller engines because they don’t take up as much room, “simpler”, and they can be included into the engine block. I consider this as a huge advantage to have, especially since jet skis work in wet and rough environments.

Some manufacturers repurpose motorcycle engines for their jet ski, which means a stator for both a motorcycle and jet ski are similar.

3 Reasons Jet Ski Use Stators

There are 3 reasons why a stator is used instead of an alternator in jet ski engines.

  • Stators are smaller.
  • Stators can be built into the engine, which cuts down on weight and costs of manufacturing.
  • Stators are simpler.

It’s interesting to note that a stator is a simplified alternator that have just enough power for small engines with electric start, like jet skis.

Saving weight, cost, and keeping it simple is the goal, and thus why jet skis use stators and don’t contain alternators.

Key Differences

The key difference between stators and alternators comes down to magnets.

When it comes to generating electricity, both play by the same rule book. They both work by moving copper wires through a magnetic field.

But here’s the twist: a stator gets its magnetic power from fixed magnets, while alternators relies on electromagnets. That’s where they really set themselves apart.

Now, the cool thing about alternators is that it can have and create their very own magnetic fields. That means its power output doesn’t depend on how fast your engine is spinning.

RPM Dependent

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.

Voltage Rectifier

A voltage rectifier, or also called a voltage regulator, takes the power produced by the stator and converts the AC (alternating current) power into DC (direct current) power and smooths it out to make it more constant and predictable for the battery and accessories.

Both a stator and alternators produce alternating current, as it’s easier to regulate the power and have better control, no matter if it’s in a jet ski or boat.

Cleans It Up

Now, here’s the deal with most jet ski stators. You see, those magnets in the stator are set in their ways – they can’t tweak the magnetic field. So, when your engine revs up and goes faster, the stator starts cranking out more electrical power. Sounds good, right? Well, not always.

The catch is, if the stator produces too much power, it can end up zapping your sensitive electrical parts or even have your jet ski’s battery get a serious fry. That’s where the voltage regulator steps in to save the day.

Think of the voltage regulator as the hero that cleans up the “electrical mess.” It takes all that power and turns it into something useful. But here’s the thing, being a hero can be tough, and the voltage regulator takes a beating over time. So, don’t be surprised if it eventually wears out – it’s all part of the job.

Signs Of A Bad Voltage Regulator

You can have one sign your jet skis voltage regulator has gone bad due to you getting a “12-Volt Low” on the display, but this could also mean the battery is bad, grounds are dirty, or a fuse is bad.

From what I have seen is that most of the jet skis electrical issues tend to be a bad battery more often then a bad voltage regulator, stator, or alternator of any kind as they do wear out even in jet skis.

Replacement

I consider replacing a jet skis voltage regulator as not being hard, it’s often next to the battery and comes off with a few screws and unplugging wires. (Most people could replace it with simple tools!)

Just make sure the jet skis battery is disconnected before you replace it.

Testing The Jet Ski Charging System

Testing the charging system of your jet ski to know if the stator or voltage regulator is working fine is similar to any other small engine. With having the jet ski out of the water, here is what you do:

  1. Connect a volt meter to the battery.
  2. You must have the jet ski engine on and look at the voltage reading.
  3. Rev the engine to 5k RPMs and look at the voltage reading.
  4. Turn the 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:

Driving Around

When I was a kid, my dad would get me to drive around on the riding mower to “charge” the battery. He was cheap and didn’t want to buy a new battery. I later in life found out this doesn’t work for riding mowers, or anything with a small engine, have a jet ski for example.

You may get a surface charge, and have the jet ski fire back up after riding for a bit, but leave it for the morning, and it won’t fire up again. There is no real alternator, so do not have any expectation of the jet ski battery to charge up.

If you’re having battery problems, the best solution is to get a new battery.

No Battery, No Go

I’ve had a few people ask me about running their jet ski without the battery in it, mostly because they need a jump and only hold one good battery.

Your jet ski won’t run without a battery, even if you swap it over once it’s running. The engine needs a place to dump its charge, and without it the engine will stop running.

What’s This About Motorcycle Engines?

I made mention in this post that some have jet ski engines that are repurposed motorcycle engines, and it’s true.

It’s not a bad thing, but when the manufacturer also makes motorcycles, which are is a far bigger market, it only makes sense to repurpose the engine for jet skis. By repurposing, they use stainless-steel bolts and other things to hold up to the corrosion and the wetter environment.

One easy way to tell if you acquired a repurposed motorcycle engine in your jet skis is to see where the oil filter is located. On a motorcycle, it makes sense to have it low and to the side. On jet skis, that would be a bad location because you got a fiberglass hull in the way. Though, you’ll see them moving the jet skis oil filter to an easier to get to location these days.

It’s not just motorcycles, either, some repurpose snowmobile engines for jet ski. It’s just an interesting tidbit, like how Ski-Doo was supposed to be Ski-Dog but due to a translation error, we got Ski-Doo. Or, at least, that’s what I’ve been told.

Jump Starting A Jet Ski?

While you can have a jump start of the jet ski, it’s best you don’t, or it can end up badly for the jet ski or your car.

Not many people realize how dangerous jump-starting any lead-acid battery is, they can explode. Also, jump-starting from your car or truck is not an idea as they output more power than the jet ski’s computer can handle, especially when the battery is completely flat.

You can jump start from a battery pack, like a jump starter kit, or even another lead acid battery not connected to anything. I cover more on this subject here.

Consider A solar Charger

If you’re having battery problems, then it’s mostly because you’re not driving your jet ski enough.

Lead acid batteries, ones used in jet ski, go flat when not used for months.

If you get yourself a solar battery charger, it will help maintain the battery and keep the jet ski ready to go on your next ride. They’re so stupid simple and effective, it makes me wonder why the jet ski manufacturers are not just baking them into the covers? Yamaha did this for a little bit with their Jet Boat line, but it never really took off.

Sum Up

This can be shocking to many riders, but your jet ski does not use a normal alternator like a car.

Your jet ski uses a stator to maintain the charge, and not an alternator to recharge the battery. While they have similarities, a stator is less powerful but fits the needs of the jet ski better.

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. This is off track from the earlier question. I have a 2003 Honda Aquatrax (sp) It’s been serviced winter and summer. Garage kept. Do have cover for it. Practically new tires on trailer. Low hours. Is it worth keeping since we don’t take it out much or should I sell it?

    Reply
    • If it’s running fine, I would keep it until it doesn’t. Honda made some great jet skis, but certain parts will be difficult to find, but you can still do the basics like an oil change and such.

      Reply

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