Jet Ski Winterization: The Complete How-to-Winterize Guide
Last spring, a customer brought in a Sea-Doo GTI that wouldn't start. He'd skipped winterization to save $60. The repair bill? $1,400 — corroded cylinders, dead battery, and a fuel system full of varnish. Jet ski winterization is not optional. I have winterized over 200 PWCs across Sea-Doo, Yamaha, and Kawasaki platforms, and this guide walks you through the exact 8 steps I use, the brand-specific gotchas that trip people up, and the mistakes I see every single year.
8-Step Jet Ski Winterization Guide
Before you start, grab these supplies: fogging oil ($10), fuel stabilizer ($10), engine oil and filter ($35-70), RV antifreeze ($5-15 for Yamaha/Kawasaki), marine grease ($10), and a smart battery maintainer ($25). Total: about $55-110. Trust me, that is cheaper than one dealer visit.
Flush the Cooling System
Connect a garden hose to the flush port. Start the engine first, then turn on the water. Idle for 90 seconds. Turn water off first, then shut down the engine.
Pro Tip: I see people do this backwards all the time — they turn the water on before starting the engine. Don't. Water can backflow into the engine and hydro-lock it. My mnemonic: engine on, water on; water off, engine off.
Change Engine Oil and Filter
Warm the engine for 2 minutes so the oil flows. PWC engines have no drain plug — you have to pump the oil out through the dipstick tube. Replace the filter and refill with brand-specific synthetic oil (XPS for Sea-Doo, Yamalube 4W for Yamaha).
Pro Tip: Sea-Doo's oil filter is tucked behind the exhaust manifold. You will scrape your knuckles. A strap wrench with a long handle saves your hands. Also, do NOT skip this step — old oil has acids that eat seals over winter.
Fog the Engine Cylinders
Remove the spark plugs. Spray fogging oil into each cylinder for 3-5 seconds. Briefly crank the engine (don't start it) to spread the oil across the cylinder walls. Reinstall the plugs. This is the step that saves your engine from springtime rust.
EFI owners, read this: Do NOT spray fogging oil into the throttle body. I had a customer do this on his Yamaha FX — fried the MAF sensor, $380 fix. Always fog through the spark plug holes, every time.
Stabilize the Fuel
Fill the tank to about 95% — not 100%. Add fuel stabilizer (STA-BIL, Sea Foam, or Star Tron). Run the engine for 2-3 minutes so the treated fuel reaches the injectors and fuel rail.
Pro Tip: Why 95% and not full? A completely full tank has zero room for thermal expansion, and on warm winter days fuel can expand and vent out. But do not leave it half-empty either — that empty space is where condensation forms. 95% is the sweet spot.
Drain Water from Exhaust and Hull
Pull the drain plugs and tilt the bow up. Let every drop out. For Sea-Doo: blow out the exhaust with compressed air at max 55 PSI through the flush port. For Yamaha and Kawasaki: flush with non-toxic RV antifreeze until pink fluid comes out the exhaust.
Pro Tip: If you live somewhere brutal like Minnesota where it hits -20°F, do not just drain — flush with antifreeze even on Sea-Doo. Also, 90% of tutorials say "buy 1 gallon of RV antifreeze." That works for most skis, but Kawasaki Ultra 310 series has a massive cooling system — get 1.5 gallons or you will run out mid-flush with antifreeze-water mix still inside.
Lubricate Pump and Steering
Grease the jet pump bearings, steering cable, and reverse mechanism. Spray corrosion inhibitor (Fluid Film or CRC Marine) on every metal surface in the engine bay.
Remove and Store the Battery
Disconnect negative first, then positive. Take the battery out of the hull and store it indoors — not on a concrete floor, put it on a shelf or wood block. Hook up a smart battery maintainer in float mode.
Pro Tip: A $25 Battery Tender Jr. pays for itself in season one. I have seen too many $160 Yuasa batteries turn into paperweights because someone left them disconnected in a cold hull all winter. Also, do not use an old-school trickle charger — it cooks the battery. You want a smart maintainer that drops to float mode.
Cover and Store
Place the ski on a trailer or storage rack on level ground. Cover with a breathable marine cover. Store in a dry, sheltered area.
Pro Tip: Do not use a blue plastic tarp. I know it is tempting — they are $8 at Harbor Freight. But tarps trap condensation, and you will pull the cover off in spring to find mold and surface rust everywhere. Spend $40 on a breathable PWC cover. Your engine bay will thank you.
Sea-Doo vs Yamaha vs Kawasaki
Here is where most people get confused. These three brands use completely different cooling systems, and getting it wrong means either wasting money on antifreeze you don't need — or worse, leaving water inside to freeze.
| Feature | Sea-Doo | Yamaha | Kawasaki |
|---|---|---|---|
| Cooling System | Closed-loop (since 2002) | Open-loop | Open-loop |
| Engine Antifreeze | ✗ Not needed | ✓ Required | ✓ Required |
| Exhaust Drain | ✓ Air, max 55 PSI | ✓ RV antifreeze | ✓ RV antifreeze |
| Recommended Oil | XPS synthetic | Yamalube 4W | OEM or aftermarket |
Bottom line: If you own a Sea-Doo 4-stroke from 2002 or newer, the engine coolant is already premixed with antifreeze in a sealed loop. You only need to drain the exhaust. Yamaha and Kawasaki? You must flush the entire system with RV antifreeze, no exceptions. I have seen too many cracked Kawasaki manifolds from people who assumed "draining is enough."
DIY vs Professional Cost
Let's talk numbers. I tracked every receipt from a full season of DIY winterization versus what local dealers charge:
| Service | DIY | Professional |
|---|---|---|
| Fogging oil + stabilizer | $20-35 | Included |
| Oil + filter change | $35-70 | $120-200 |
| Antifreeze flush | $5-15 | Included |
| Battery tender | $25-40 | $25-40 |
| Total | $55-110 | $150-1,000+ |
The math speaks for itself. Dealer labor runs $100-150/hour, and that is where most of your money goes. Your first DIY winterization takes 2-4 hours. By year two, you will be done in 90 minutes. For first-time riding safety after dewinterization, check our jet ski safety for beginners guide.
Remember that customer who skipped winterization to save $60? His $1,400 spring repair could have paid for 12 years of DIY supplies. Do not be that guy.
5 Mistakes I See Every Single Year
These are not theoretical. These are the top 5 calls I get every March when people try to start their skis and nothing happens:
| Mistake | What Happens | Do This Instead |
|---|---|---|
| Not fogging the engine | ✗ Cylinder rust, low compression, won't start | ✓ Fog through spark plug holes, every time |
| Leaving old fuel untreated | ✗ Gum clogs injectors, $200-400 fuel clean | ✓ Fill 95% + add stabilizer + run engine |
| Battery left in the hull | ✗ Self-discharge and sulfation kill it dead | ✓ Pull it, store indoors, hook up tender |
| Skipping hull water drain | ✗ Freeze expands, cracks hull or panels | ✓ Pull plugs, tilt bow, let it all out |
| Using a plastic tarp cover | ✗ Traps condensation, mold and rust everywhere | ✓ Spend $40 on a breathable marine cover |
Hull Protection During Storage
Here is something most winterization guides completely ignore: your hull takes a beating in storage too. Temperature swings cause gelcoat to expand and contract. And if you stack skis next to each other in a garage — which most people do — they bump into each other and scratch.
This is actually one of the reasons we designed the AirJain inflatable collar in the first place. We kept seeing customers pull their skis out of storage with fresh gelcoat gouges from trailer frames and neighboring watercraft. The collar wraps most of the upper hull in an inflated cushion — not just for water protection, but for storage safety too. It bolts on with factory hardware, so it stays put in cold weather unlike adhesive foam bumpers that peel off when temps drop.
Want to see how it compares to traditional fenders? Check our collar vs fender breakdown, or follow our step-by-step install guide before the ground freezes.
A collar costs $799-$1,199 and lasts 5-8 years. A single gelcoat repair from a storage scratch runs $200-800. You do the math.
Frequently Asked Questions
When should I winterize my jet ski?
Before the first hard freeze, or whenever you know you are done riding for 60+ days. In northern states, that is usually late October to mid-November. Even in warm climates like Florida, if the ski sits for more than 2 months, do the fuel stabilizer and fogging steps — fuel still goes bad and cylinders still rust in the heat.
Does Sea-Doo need antifreeze for winterization?
Sea-Doo 4-strokes since 2002 use a closed-loop cooling system, so the engine itself does not need antifreeze. But the exhaust system and intercooler (on supercharged models) still use raw water and must be drained. Yamaha and Kawasaki use open-loop cooling and require a full RV antifreeze flush. If you are not sure which system you have, check your manual — do not guess.
How much does jet ski winterization cost?
DIY runs $55-$110 in supplies. A dealer charges $150-$300 for basic service, and $300-$1,000+ if you add oil change, spark plugs, and supercharger inspection. DIY saves you 60-80%. The only thing I would not skimp on is the battery maintainer — that $25 tender is the best investment you can make.
Do 4-stroke jet skis need fogging oil?
Yes, absolutely. I do not care what your buddy at the boat ramp told you — 4-stroke cylinder walls are bare metal and will rust over the winter. Fog through the spark plug holes, never through the throttle body on EFI engines unless you want to buy a new MAF sensor.
What happens if I don't winterize my jet ski?
Fuel turns to varnish and clogs your injectors. Cylinder walls rust and compression drops. Trapped water freezes and cracks exhaust manifolds. The battery dies. Repairs range from $300 for a battery and fuel system clean to $2,000+ for a cracked engine block. I have seen it happen every spring, and it is always preventable.
Should I fill or empty the gas tank for winter?
Fill it to about 95%. A full tank minimizes air space where condensation forms, but leave a little room for thermal expansion. Always add stabilizer and run the engine for 2-3 minutes so the treated fuel circulates through the injectors and rail.
Questions or thoughts?
If you have any questions or thoughts, leave a comment below — we usually reply within 24 hours.
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