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Outboard Winterizing Checklist

Pick the motor. You get every step its maker publishes for laying it up, in the order the jobs have to happen — with the maker’s own words under each one, and the spring list on the other tab.

Which end of the season?
Where does the fuel spend the winter?

4-stroke on the transom · treated fuel · away from the house

22 steps, in this orderFuel first while it can still run, then oil and fogging — after which it does not run again — the gearcase before anything freezes, and the motor left vertical. Under each step are the words of the maker who published it: Mercury, Yamaha, Honda, Tohatsu and BRP (Evinrude).

Fuel is handled outdoors with the engine cold, and nothing runs without cooling water — a hose on muffs, a test tank or the lake. This list is what the makers publish; the manual that came with your motor outranks every line of it, and a job you are not sure of is a dealer’s job.

Every maker’s document was read 2026-09-26. The manual that came with your motor outranks every line here.

For the logbook (optional)
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Printed at the top of the list, and kept on this device only.

The lay-up list

1 · Fuel — first, while the engine can still run

  • Mercury — the original words

    Mercury: “If the fuel in your tank is more than a month old and it’s too late in the season to use it up, have it pumped it out and replace it with fresh fuel.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Mercury, on newer tanks: “Because newer tanks can’t freely vent to the atmosphere and won’t collect moisture from the air, they don’t need to be filled.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Mercury — the original words

    Mercury: “If you have an older boat with a vented fuel tank, it’s a good idea to fill the tank with fresh fuel to keep condensation from forming in the tank. Stop when the tank is about 95 percent full because extreme temperature changes over the winter can cause the fuel to expand, potentially forcing gas out of the vent.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “Then add the correct amount of fuel stabilizer to the fresh fuel.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Yamaha: “Add a fuel stabilizer to your fuel tank to keep the fuel fresh throughout the winter.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “It is important to get that treated fuel into the entire fuel system by running the boat for about 10 minutes, either in the water or while connected to a garden hose (follow owner’s manual instructions if using a hose).” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “Finally, replace the fuel filter.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Yamaha: “Replace your fuel filter by unscrewing and putting in the new filter. Dispose the old filter and fuel properly.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

2 · Oil and fogging — the last time it runs

  • Honda — the original words

    Honda: “After each use in salt water or dirty water, thoroughly clean and rinse the outboard motor with fresh water.” Honda Marine BF2.3DH Owner’s Manual — Storage · read 2026-09-26

  • Mercury — the original words

    Mercury: “If you have a four-stroke outboard, the engine oil and filter should be changed every 100 hours or once a season, regardless of how many hours the engine was used.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Yamaha: “Check the old oil for discoloration or a foamy residue, which is an indication that water could be getting into the lower unit through a damaged seal.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

    Honda: “Change the engine oil (p. 42 – 44).” Honda Marine BF2.3DH Owner’s Manual — Storage · read 2026-09-26

  • Mercury — the original words

    Mercury: “After you change the oil, it’s always a good idea to start the engine again, to circulate fresh oil through the engine and to check for leaks” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Yamaha does it through the fuel instead: “Pete uses a portable fuel tank with a small amount of fresh gas treated with Yamalube Ring Free, PLUS EFI Engine Storage Fogging Oil and Yamalube Fuel Stabilizer & Conditioner PLUS.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

    Mercury — the original words

    Mercury: “Ideally while the motor is still warm, treat four-stroke and conventional two-stroke engines with fogging oil to prevent corrosion within the engine. Remove the spark plugs and spray the fogging oil directly into each cylinder, following the directions on the can.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “Hurney recommends putting a coat of anti-seize lubricant on the spark plug threads before carefully replacing the plugs. Use new spark plugs, correctly gapped, per the service schedule in your owner’s manual.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

3 · Gearcase and propeller — before anything freezes

  • Mercury — the original words

    Mercury: “Any water in the gear lube can freeze and expand during storage, potentially cracking the gearcase. As you drain the old lube, inspect it carefully. If gear lube appears white or creamy, it may indicate the presence of water in the lubricant.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Yamaha: “Do not attempt to fill from the top.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

    Tohatsu: “Change the gear oil in the gear case (See page 50).” Tohatsu M4C / M5B Owner’s Manual — Off-season storage · read 2026-09-26

  • Mercury — the original words

    Mercury: “If water is suspected to be present in the gearcase, a pressure check of the gearcase should be completed by an authorized dealer.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “Over time, the forward thrust of the propeller presses the line into the rubber propshaft seal. If the seal is damaged, water can enter the gearcase and cause significant damage.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    Yamaha: “The most common cause of this problem is picking up discarded fishing line behind the propeller.” Yamaha Outboards — How to Winterize Your Yamaha Four-Cylinder Outboard · read 2026-09-26

  • Mercury — the original words

    Mercury: “Always coat the propshaft with a quality marine grease such as Mercury 2-4-C Marine Lubricant before reinstalling the prop, and tighten the prop nut to the torque specification listed in the owner’s manual.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

4 · Grease, anodes and the outside

5 · Battery

  • Mercury — the original words

    Mercury: “Be sure the battery is fully charged, remove it from the boat, and store it in a cool, dry place. Storing the battery on a maintenance charger will keep it charged and fresh until spring.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

6 · Where it spends the winter

  • Mercury — the original words

    Mercury: “Whether the boat is stored on a trailer or a rack, the motor should be trimmed down to its vertical position so that any water remaining in the engine can self-drain. If water trapped in the engine freezes, it could cause serious damage.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

    BRP (Evinrude): “Never place the gearcase higher than the powerhead. Any water remaining in the exhaust passages can run into the cylinders and cause serious damage.” BRP Evinrude E-TEC 200/225/250 Operator’s Guide — Storage and Pre-Season Check · read 2026-09-26

  • Mercury — the original words

    Mercury: “In some situations, mice can be a problem – they may be able to get under the motor cowl and chew on wiring.” Mercury Marine — How to Winterize Your Outboard · read 2026-09-26

  • Honda — the original words

    Honda: “Cover the outboard motor to keep out dust. Do not use a plastic sheet as a dust cover. A nonporous cover will trap moisture, promoting rust and corrosion.” Honda Marine BF2.3DH Owner’s Manual — Storage · read 2026-09-26

Quick answer: winterize an outboard in this order. Fuel first, while the engine can still run: fresh fuel, stabiliser at the label’s dose, and about 10 minutes of running on water so the treated fuel reaches the carburetor or injectors. Then the oil on a four-stroke, then fog it — and after the fog it does not run again. Then the gearcase: drain the gear lube and look at it before anything freezes, because white or creamy lube means water, and water in a gearcase can freeze and crack it. Battery off the boat, and the motor trimmed down to vertical so the water in it drains. Two exceptions catch people out: Mercury says a direct-injection OptiMax gets DFI oil in each cylinder, not fogging oil, and an Evinrude E-TEC fogs itself.

Why the order matters more than the list

Every winterizing list online has roughly the same jobs on it. What most of them get wrong is the order, and on an outboard the order is the whole trick, because several jobs can only happen while the engine is still allowed to run and one job ends that for the winter.

  • The stabiliser has to be run through. Stabiliser in the tank protects the tank. The fuel that goes stale over winter is the fuel sitting in the carburetor bowl or the injector rail, and the only way to get treated fuel there is to run the engine — Mercury says about ten minutes, in the water or on a hose.
  • Fogging is the last time it runs. Fogging oil coats the cylinders so they do not rust. Run the engine afterwards and you burn the coat off. So the fuel job and a four-stroke’s post-oil-change leak check both come before it, never after.
  • The gearcase is about freezing, not about oil. The reason the gear lube comes out in autumn rather than spring is that water hiding in it expands when it freezes. Look at what drains: white or creamy means a seal is letting water in, and that is a pressure test at the dealer, not a refill and a hope.
  • Vertical is the last thing, and it matters. A motor left tilted up holds water in places it can freeze. Trimmed down, it drains.

How each kind of outboard is fogged

The step that differs most between engines, in each maker’s own terms
MotorFogging, per the makerOil change?Whose words
4-stroke on the transomFogging oil sprayed into each cylinder, plugs out — or, Yamaha’s way, fogging oil mixed into a small tank of fuel and run throughYes, and the filterMercury, Yamaha
Carbureted 2-strokeFogging oil into each cylinder through the plug holesNo — no crankcase oilMercury
Mercury OptiMax (DFI)No fogging oil. One ounce of DFI outboard oil into each cylinderNoMercury
Evinrude E-TECThe engine’s own winterize mode fogs it — about a minute, then it stops itselfNoBRP
Portable 4-strokeA teaspoon or two (5–10 cc) of engine oil into the cylinder, starter pulled slowlyYesHonda
Portable 2-strokeA teaspoon of engine oil or storage spray into the cylinder, and the carburetor drainedNoTohatsu

The OptiMax row is the one worth reading twice. The standard advice — spray fogging oil in — is exactly what Mercury tells you not to do on a direct-injection engine.

Where the makers do it differently

Where two makers publish different ways of doing the same job, the checklist shows both and names who says what. There are three:

  • Fogging. Mercury sprays it into each cylinder. Yamaha’s technician runs it in with the fuel from a small portable tank. Both are the makers’ own methods; your manual says which one your engine wants.
  • A full tank. Mercury’s advice is to fill an older, vented tank to about 95% so less air condenses in it — and it says newer sealed tanks do not need filling. Honda and Tohatsu both say to fill a portable tank when you add stabiliser.
  • Lying a portable down. Tohatsu says stand it upright. Honda allows its small motor to lie down with the tiller handle up. Either way, only the position your own manual shows — any other can let oil or water go where it should not.

Spring, on the other tab

The spring list is shorter and it has one rule that outranks the rest: water to it before it starts, not even a brief start without it. After that you are watching for two things — the puff of smoke on the first start, which is the storage oil burning off and is expected, and a steady stream from the water-pump tell-tale. No stream, engine off. If you want the reasons a tell-tale goes quiet, they are in Outboard Not Peeing? Check These in Order.

More on the jobs themselves

FAQ

What is the right order to winterize an outboard?
Fuel first — stabiliser in fresh fuel, run about 10 minutes on water so it reaches the carburetor or injectors. Then the engine oil and filter on a four-stroke, then fog it; it does not run after that. Then the gear lube, drained and looked at for water before anything freezes. Grease and anodes, battery off the boat, and the motor trimmed down to vertical last.
Do I need to fog a four-stroke outboard?
Mercury says yes — its guide treats four-strokes and conventional two-strokes the same, fogging oil into each cylinder while the motor is still warm. Yamaha fogs its four-strokes too, through the fuel system from a portable tank. Your manual says which method your engine wants.
Should I fog an OptiMax or an E-TEC?
Not with a can of fogging oil. Mercury says a direct-injection engine like the OptiMax gets one ounce of DFI outboard oil into each cylinder instead. An Evinrude E-TEC has its own winterize procedure that fogs the engine itself in about a minute; BRP’s operator’s guide gives the throttle sequence, and the checklist quotes it.
Should I leave the fuel tank full or empty over winter?
Mercury says fill an older vented tank to about 95% so less moisture condenses, and that newer sealed tanks do not need filling. Honda and Tohatsu say to fill a portable tank when you add stabiliser. Either way, treat the fuel and run it through. Honda also publishes draining the tank and carburetor completely as the alternative for its small portables.
Why does the lower unit oil have to be changed before winter?
Because of freezing, not because of age. Water that has got into the gearcase past a seal sits in the lube, and when it freezes it expands — Mercury’s guide warns it can crack the gearcase. Draining it in autumn gets the water out and shows you whether a seal is leaking: milky or creamy lube means water, and a pressure test before spring.
Can I winterize an outboard on the trailer?
Yes, as long as it has cooling water whenever it runs — flushing muffs or a flushing port with the hose turned on, or a test tank. BRP says the propeller comes off and the engine stays in neutral for the E-TEC’s winterize run; Honda says the same about the propeller for a portable run on land.