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August 26, 2026 4 min read
Every fall, our customer chat fills up with questions about winterizing — "should I fog it?", "what's the difference between flushing and winterizing?", "do I need antifreeze?" If you're putting your jet ski to bed for the winter and want it to start up cleanly in spring, this guide covers every step, in order.
Before anything else, let's clear up the most common confusion we see:
Perform a thorough flush as your first step. Connect your flush kit to the hose fitting, run fresh water for 3–5 minutes at idle, then shut down the engine while water is still running to allow the pump and cooling passages to clear. Do not rev the engine while flushing — the impeller can suck air and cavitate without being in water.
Do this before storage, not in spring. Used motor oil becomes acidic over time, and acidic oil sitting against engine internals all winter causes corrosion. Fresh oil going into storage means clean, neutral oil protecting those surfaces for 4–6 months. Replace the oil filter at the same time.
2-stroke engines: check and top off the oil injection reservoir. If your 2-stroke uses premix, drain the remaining fuel from the tank and run it dry before storage.
Fogging applies a protective coating to cylinder walls, pistons, and upper engine components to prevent corrosion during storage. This is especially important in humid climates.
With the engine running at idle, spray fogging oil directly into the carb inlet(s) while slowly throttling up, then shut down. The smoke is normal — you're coating the cylinder walls.
The procedure varies by model. Some 4-strokes are fogged through the throttle body air intake; others have specific fogging procedures in the service manual. Check your manual or contact us — fogging a 4-stroke incorrectly can hydrolock the engine if you introduce too much oil into the combustion chamber.
For newer fuel-injected 4-strokes (2015 and newer Sea-Doos, most modern Yamahas), some manufacturers actually recommend against traditional fogging and instead rely on the fresh oil change to protect internals. Follow your owner's manual here.
Add marine-grade fuel stabilizer to a full tank of fresh fuel. A full tank minimizes the air space where condensation can form. Run the engine for 5–10 minutes after adding stabilizer to distribute it through the entire fuel system, including carburetors or injectors.
Ethanol-blended fuel (E10) degrades quickly — within 30–60 days it can varnish carb jets and injectors. Stabilizer extends this to 12+ months for storage.
If your ski has carburetors, consider draining the float bowls completely after running stabilized fuel through them. This prevents varnish buildup in the jets.
A battery left to discharge completely over winter may not recover. Options:
Most modern jet skis use raw water (lake or ocean) cooling — there's no enclosed coolant system that can freeze. The water you need to worry about is any left trapped in cooling passages after shutdown.
Your final flush should push most water out. In climates where temperatures drop below 25°F, consider blowing out any remaining water with compressed air through the flush fitting, or add a small amount of non-toxic RV antifreeze to the cooling system via the flush port (not engine coolant — RV-type antifreeze safe for drains).
Some supercharged Sea-Doos (RXP-X, GTX Limited) have an intercooler cooling loop that is a closed freshwater system — that system does need monitoring in hard-freeze conditions.
Indoor storage is always preferable — it protects from UV, precipitation, and extreme temperature swings. If outdoor storage is your only option, elevate the trailer slightly nose-up so any water that enters the hull drains toward the rear drain plug (which should be open). A high-quality UV-rated cover is non-negotiable for outdoor storage.
Find flush kits, fogging oil, fuel stabilizer, battery tenders, and storage covers for your specific model at WatercraftSuperstore.com.