How to Dewinterize Your Jet Ski in Spring: Step-by-Step Guide | PWCParts.com

If you can smell the lake from your driveway, it's time. After months under a cover with stabilized fuel and fogged cylinders, your jet ski needs a proper wake-up call before the first ride of the season. Skipping dewinterization is the fastest way to turn a 70-degree Saturday into a tow back to the ramp. At PWCParts.com we ship consumables for thousands of spring tune-ups every April and May, and riders who do this right rarely call us in July with a fouled plug or a smoked impeller. Here's exactly how we do it on our own Yamaha WaveRunners, Sea-Doos, and Kawasaki Jet Skis.

Step 1: Inspect Before You Touch a Single Bolt

Before you start pulling parts, walk around the ski with a flashlight. Look for cracked hoses, mouse damage in the engine bay (it happens more than you'd think), corrosion on the battery terminals, and any oil or coolant pooling in the bilge. If you stored the ski outside, peel back the seat and check the foam under the gas tank for moisture. Catching a chewed fuel line or a swollen battery now saves you from discovering it 200 yards offshore. Make a quick punch list of what needs attention, then head into the actual service.

Step 2: Battery — Test, Charge, or Replace

A jet ski battery that sat through a New England winter without a tender is rarely happy. Pull the battery out of the ski, clean the terminals with a wire brush, and put it on a smart charger overnight. After a full charge, load-test it. If it can't hold above 12.4 volts under load, replace it now — don't gamble. While the battery is out, inspect the cables and the ground strap for green corrosion and replace the terminal bolts if they're chewed up. Reinstall with a thin coat of dielectric grease on the posts.

Step 3: Change the Oil and Oil Filter

If you didn't change the oil during winterization, do it now. Acid byproducts in old oil eat at bearings while the engine sits, so fresh oil is non-negotiable for a four-stroke before its first start. Run the engine on the hose for a couple of minutes to warm the oil, shut it down, then extract through the dipstick tube with a hand pump. Replace the oil filter at the same time — never reuse an old one. Kawasaki owners can grab the OEM 4-stroke filter from our Kawasaki Jet Ski 4-Stroke Oil Filter 16097-0008 page, and we stock matching kits for STX-15F and Ultra series in our Kawasaki Jet Ski Oil Change & Maintenance Kits collection. Fill with manufacturer-spec 10W-40 marine oil, run for 30 seconds, shut down, and check the level cold.

Step 4: Pull and Replace the Spark Plugs

Even plugs that looked fine in October can foul from condensation, fogging oil, and ethanol residue over winter. New plugs cost less than a tank of gas and they make the difference between a ski that fires on the first crank and one that floods on the trailer. Gap them to spec (most modern PWCs run NGK CR9EB or similar at 0.030"), torque them to 13 ft-lb, and reinstall the coil-on-plug caps with a dab of dielectric grease. We carry the right plugs for every major model in our jet ski spark plugs section.

Step 5: Drain Old Fuel and Inspect the Fuel System

Stabilized 91-octane that sat all winter is still old fuel. If you have less than half a tank, top it off with fresh premium and a fuel system cleaner. If the tank is more than half full of old gas, siphon it down. Inspect the fuel lines for cracking near the clamps — ethanol-blended pump gas eats older rubber lines faster than people expect. Check your in-line fuel filter and replace it if it looks dark or has any debris. While you're in the engine bay, give the air filter a once-over and replace it if it's collapsed or contaminated.

Step 6: Cooling System, Pump, and Hull Check

Check cooling hoses for soft spots and white residue (a sign of past overheats). Spin the impeller by hand — it should turn smoothly with no grinding. Inspect the wear ring for galling and the impeller blades for nicks; even small dings hurt top speed. Eyeball the hull for stress cracks around the bond rail and re-seat the drain plugs with fresh O-rings.

Step 7: First Start on the Hose

Hook up the flush adapter, start the engine, then turn on the water — never the other way around. Let it idle for 90 seconds while you listen for unusual noises and watch for steady pee-stream flow. Shut water off first, then the engine, and blip the throttle to clear the exhaust. Trailer to the ramp and do an easy 10-minute shakedown ride before opening it up — catch any leaks while you're still close to the dock.

Frequently Asked Questions

How long does it take to dewinterize a jet ski?

Plan on two to three hours for a thorough job, plus overnight for the battery to charge. If you're replacing oil, plugs, and filters at the same time, budget closer to half a day. It's faster on subsequent skis once you have the tools laid out.

Do I really need to change the spark plugs every spring?

Yes — and it's the cheapest insurance you can buy. Plugs degrade from condensation and fogging oil over the off-season, and a fresh set makes cold starts effortless. At a few dollars per plug, there's no reason to gamble.

Can I use car oil in my jet ski?

No. Marine-spec four-stroke oils have additive packages designed for the high-RPM, wet-environment service that PWC engines see. Automotive oil can cause friction-modifier issues with wet clutches and won't shed water the same way. Always use the viscosity and spec called out in your owner's manual.