How to Winterize Your Jet Ski (Complete Checklist)

The riding season is over and it's time to put the ski away. Winterization is one of those jobs that's easy to put off — and one of the most expensive to skip. A cracked engine block from a freezing coolant line, a gummed-up fuel system, or a dead battery from sitting discharged all winter can each cost more to fix than the entire winterization process. Do it right once and your ski comes out of storage in spring ready to ride.

This checklist applies to all major PWC brands: Sea-Doo, Yamaha WaveRunner, and Kawasaki Jet Ski. Brand-specific notes are called out where relevant.

The Complete Jet Ski Winterization Checklist

1. Flush the Cooling System

This is the most critical step, especially if you ride in salt water. Connect a flush adapter to the flush port on your ski (every modern PWC has one), attach a garden hose, and run the engine at idle for 2–3 minutes with fresh water flowing through the cooling system. This purges salt, sand, and minerals from the cooling passages that would otherwise corrode or clog them over winter.

After flushing, turn off the water supply before shutting off the engine — this lets the engine pump expel remaining water from the cooling lines so nothing sits and freezes.

Sea-Doo note: BRP recommends a specific flushing procedure using the flush fitting on the hull. Consult your operator's guide for your model's exact flush port location.

Never run the engine for more than 15–20 seconds without water flowing through the flush adapter — PWC engines have no cooling without water and will overheat rapidly out of the lake.

2. Fog the Engine

With the engine still warm from the flush, remove the air intake/flame arrester and spray fogging oil directly into the throttle body while briefly revving the engine. This coats the cylinder walls, intake valves, and combustion chambers with a protective oil film that prevents corrosion during storage. Without fogging, bare metal cylinder walls can rust over a long winter, especially in humid climates.

After fogging, reinstall the flame arrester and place a rag loosely over the intake opening to keep rodents and moisture out.

3. Stabilize the Fuel

Old gasoline is one of the top causes of hard-start and no-start problems in spring. Modern ethanol-blended fuel starts degrading in as little as 30 days. Add a quality marine fuel stabilizer to a full tank of fresh fuel (fill it up before storing — a full tank prevents moisture condensation inside the tank). Run the engine briefly to circulate the stabilized fuel through the fuel lines and injectors.

Do not drain the fuel system completely — dry rubber seals and o-rings in the fuel system can crack over winter. A full tank with stabilizer is the correct approach.

4. Change the Oil and Filter

Used engine oil contains combustion byproducts and acids that will attack internal engine components if left sitting for months. Change the oil and filter before storage, not in spring. Fresh oil means your engine is sitting in clean, protective fluid all winter rather than acidic used oil.

Check your owner's manual for the correct oil specification — most 4-TEC Sea-Doos and Yamaha 4-stroke WaveRunners use a specific PWC or marine 4-stroke oil. Do not substitute automotive oil.

5. Inspect and Service the Pump

While the ski is out of the water, take 10 minutes to inspect the jet pump:

• Hand-spin the impeller — should feel smooth and quiet
• Check the wear ring for grooves or scoring
• Look at the impeller blades for chips or damage
• Check the intake grate for cracks or missing fasteners
• Replace the zinc anode if it's more than 50% consumed

Better to discover a worn wear ring in November than to find it when you launch in May. Order parts over the winter and have them ready for a spring install.

6. Flush and Lubricate the Exhaust System

After running the flush procedure, the exhaust system also needs attention. With the ski on the trailer, tilt the nose up slightly so any remaining water in the exhaust drains out the back. On Sea-Doos with a waterlock muffler, water can sit and freeze if the ski is stored level or nose-down.

Spray a light coat of corrosion inhibitor (like Corrosion Block or similar marine product) into the exhaust outlet to protect the stainless and rubber components inside.

7. Remove and Maintain the Battery

A jet ski battery left in the hull over winter will self-discharge and sulfate, permanently reducing its capacity. Remove the battery entirely:

• Clean the terminals with a wire brush and apply dielectric grease
• Store the battery somewhere above freezing (garage shelf, basement)
• Connect it to a battery tender or smart charger set to maintenance mode — this keeps it at full charge without overcharging

A battery tender costs $20–30 and can extend battery life by years. A replacement jet ski battery costs $80–$150. The math is straightforward.

8. Lubricate All Grease Fittings and Moving Parts

With the ski on the trailer, grease all fittings with marine-grade grease:

• Steering cable end fittings
• Reverse mechanism pivot points (if equipped)
• Handlebar pivot and tilt mechanism
• Any exposed cable ends

Apply a corrosion inhibitor spray to any exposed metal hardware on the hull exterior, trailer bunks, and tie-down hardware.

9. Clean the Hull and Inspect for Damage

Give the ski a thorough wash inside and out. Open the storage compartments and dry them completely — trapped moisture breeds mold. Inspect the hull for cracks, especially around the intake grate and pump tunnel where debris strikes happen.

Small gelcoat cracks are easy to repair over winter. Large cracks or delamination should be addressed before spring — water intrusion into the hull foam is serious.

10. Cover and Store Properly

• Use a fitted cover — a tarp that pools water is worse than no cover
• Store on the trailer with the nose slightly elevated so any residual water drains out the back of the hull
• If storing indoors, leave the storage compartment lids cracked slightly for airflow
• Keep away from direct sunlight if storing in a garage with windows — UV accelerates gelcoat fading even in winter
• If storing outdoors, loosen the tie-downs slightly so the hull isn't under constant stress from strap tension

Winterization Timing: When Should You Do It?

Do it before the first freeze in your area, not after. The critical issue is water trapped in the cooling system, exhaust, and pump — any of these can crack when water freezes. In most of the continental US, completing winterization by mid-October is safe. In the northern states, aim for early October. In Florida and other warm climates where freezing is rare, the fuel stabilizer and pump inspection steps are still important even if freeze protection is less of a concern.

Parts to Have on Hand for Spring

Winterization is also the best time to assess what the ski needs before next season. Common parts to order now so you're ready to ride in spring:

• Spark plugs (replace every 2 seasons as a matter of course)
• Oil and filter for the spring oil change
• Wear ring or impeller if your pump inspection flagged them
• New battery if yours is more than 3–4 years old
• Fuel filter if it hasn't been changed recently

Browse maintenance parts and fluids or shop engine parts to get your order in over winter and be ready for a first-day-of-season launch.

Bottom Line

Winterization takes 2–3 hours and costs very little in materials. Skipping it and having to repair a cracked block, replace a fuel pump, or buy a new battery in spring costs $300–1,000+. Do the checklist, do it before the first freeze, and your ski will be ready to go the moment the water warms up.