How to De-Winterize a Jet Ski – 11 Simple Steps

The new riding season is starting, and soon enough we’ll be hitting the water with our jet skis.

Since many jet skis were winterized a few months ago, we’ll need to de-winterize them.

Let me walk you through what I do to de-winterize a jet ski before the riding season.

1. Charge Your Battery

Before you do anything, now is a good time to charge your jet ski battery if you have not done so already.

I have a love-hate relationship with jet ski batteries. If anything is going to give you trouble at the start of the jet ski riding season, it’s more than likely going to be the battery.

I will always try charging the jet ski battery using a smart battery charger the night before I do my de-winterizing.

The next day I disconnect the battery charger, and before I put it in the jet ski, I like testing it with a load tester (Amazon Link Ad). I’ve had batteries that say they charged or seemed fine, but when I put it in, it was dead. So to keep myself from doing the same job twice, I test the battery before putting it in the jet ski.

2. Change Spark Plugs

I like changing the spark plugs in my jet skis once a year.

Stick to the spark plugs your manufacturer recommends. Do not get fancy spark plugs; I’ve found they’re not as good as the simple and often cheaper spark plugs the owner’s manual suggests. Also, the plugs the manufacturers say to get are pre-gapped; no need to mess with that either.

The process of winterizing your jet ski can cause the old plugs to foul.

Not only that, but changing the spark plugs on your jet ski is simple and cheap to do.

Changing the spark plugs once a year keeps you from having issues in the future with spark plugs going out. Jet ski engines take a lot more abuse than your car’s engine, so I tend to change the spark plugs more often.

3. Add Fresh Gas

How much gas you keep in a boat or jet ski for the winter is a hotly debated topic.

I store it near empty (two bars or less) with the correct amount of fuel stabilizer because when the season starts, I can fill up the tank with premium gas.

During the winter months, the gas may go bad or attract water. The more gas you have, the more it will attract water. So I keep my fuel level low, and at the start of the season, I add premium gas on the first fill up to help even it out.

If I had a full tank and the gas went bad, I would have to suck it out, which seems like a waste to me. I also don’t like having a tank full of gas sitting near my home all winter, either.

But like I say, everyone has their own opinion on the topic, but this is what I do, and it seems to work well for me.

Note: I typically run regular or whatever the manufacturer suggests for my non-supercharged jet skis. But for supercharged jet skis, I will always run premium even if the manufacturer says you can get away with regular. Jet ski engines are high-performance engines and do better with premium gas for supercharged models.

4. Change The Engine Oil And Oil Filter

If you didn’t change the oil during the winterization, now would be a good time.

Don’t wait until the middle of the riding season as dealerships get weeks behind, and parts also start to get limited when they get busy.

Changing the oil before the riding season or during the winterization is also a personal preference. I tend to do it during the winterization because parts and labor are often cheaper in the winter. While the jet ski sits, I like it with fresh new oil and not old oil that has become contaminated and acidic. But doing your oil change now is not bad; many like doing it now as you start the season with fresh oil.

Either way, it honestly doesn’t matter; just make sure you at least change the oil and oil filter in your jet ski once a year along with the spark plugs.

5. Check Drain Plugs

The drain plugs are often overlooked by many owners, and it’s one of the more essential components of your jet ski.

Before the riding season, and even before you put it in the water, you should check your drain plugs.

If the drain plugs are damaged, or the o-ring is damaged or missing, you need to get a new drain plug (or o-ring).

A damaged drain plug or its o-ring can cause your jet ski to sink, so you must check them often.

6. Check Sacrificial Anode

Something else to check when you’re looking at the drain plugs is the sacrificial anode.

The sacrificial anode is a piece of metal that often looks like a tiny metal donut with a bolt through the middle. It’s located at the rear of your jet ski, close to your pump and nozzle.

The purpose of the sacrificial anode is to erode more than the other metal parts of your jet ski. Without that sacrificial anode, the exposed metal of your pump will start to erode much faster, causing things like steering or reverse not to work correctly. It gives up itself to protect your jet ski.

Ensure to check the sacrificial anode for damage and replace it if it is damaged or missing.

7. Check Coolant

This is only for Sea-Doo’s as they use a closed-loop cooling system, but make sure to check your coolant levels.

Check the overflow tank to see how much coolant you have. You will have a high and low bar on the tank; you want to be between the two.

Important: You have different types of coolants depending on the year of your Sea-Doo, one is green, and the other is orange/pink. Never mix the two; if you have green coolant, only add the green coolant. If you’re not sure what coolant you have, ask your dealer. Mixing these two coolants can create a gel that clogs the cooling system and makes a big mess that will need to be fixed.

8. Check Your Trailer

Let’s not forget to check your jet ski trailer too.

Ensure you have the correct air pressure in your tires and grease the bearings. Ideally, you should grease your trailer bearings every year or however many miles your trailer’s manufacturer recommends.

Here is a great video showing you how to grease the bearings of a trailer.

Don’t forget to check the trailer lights and any damage to the trailer.

Replace any straps that have torn or become too faded by the sun. That front bow strap is one to pay attention to; I’ve had a few snap on me when driving. I even had a few guys front bow straps snap, and since they had no rear straps, the jet ski ended up in the road. This is why I’m so stern about rear straps.

New straps will be cheaper than fixing fiberglass, that is for sure, so if your straps are over 3 years old, damaged, or very faded by the sun, you should go ahead and replace them.

You can get front winch straps here (Amazon Link Ad).

You can get rear straps here (Amazon Link Ad).

9. Wash Your Jet Ski

Before heading to the water, I like to give the jet ski a good wash. Marine soap works best but car soap will work too.

Since the jet ski will be sitting more in the sun now that it’s getting ready for the season, I like spraying the seat with a vinyl protectant (Amazon Link Ad).

The seats are made of vinyl, and if it gets dry or sun-damaged, it tends to tear or leave annoying black spots that look like mold. Spraying vinyl protectant every time I can remember does help protect the seats.

10. Check For Leaks

Before driving the jet ski, I like to back it into the water still attached to the trailer and truck then run the engine. Make sure the drain plugs are in too!

I keep both front and rear straps on, I only want to see if it takes on water, so I don’t fully back it in, just enough so the pump can suck up water.

Make sure you’re not doing this close to rocks or sand. Beaching a jet ski to do this test is a no-no.

I leave the seat off and just let it idle for a minute to see if it takes on water.

Do not rev the engine; just let it idle for a minute and see if it’s taking on water. Keep the handlebars straight too.

This leak test will also show if any other problems have come up. For example, if the jet ski doesn’t start and idle with it half in the water, it will be even worse if you try to launch it fully.

Since I’m already at the water and if it passes my test it’s nothing to get it ready for a real ride, this is why I like doing it this way.

If you feel more comfortable you can run it from the garden hose at your home instead. Just make sure to have the engine on before turning the hose on and turn the hose off before turning the engine off.

11. Water Test It

When the jet ski passes the leak test, the next thing to do is take it out on the water and ride.

Spend the first 5 minutes of your ride going easy and if everything seems fine, ride it like normal.

As soon as the jet ski is started in water, it’s been officially de-winterized. So if you want to winterize it again for some reason, it will need to do so after it’s been run in the water.

Let The Dealership De-Winterize Your Jet Ski?

You honestly don’t need the dealership to de-winterize your jet ski.

The most complicated thing is replacing the spark plugs and/or changing the oil. If you have the dealership do that for you already, letting them do a full de-winterize is fine.

To be honest, what most dealerships do to de-winterize a jet ski is connect the battery, change the spark plugs, and run it on the hose. Most people can do that themselves, so no real need to have the dealership do it for you unless you want them to.