Owners Tips

How to Winterize Your Boat

When the leaves turn orange, for most boat owners it means it's time to winterize. It can seem a thankless task – certainly a lot less fun than getting the boat ready to play in the springtime – but your boat needs attention in the fall more than at any other time, and it'll reward every hour of effort now with two hours less work in the spring.

Don't think you're immune just because you live on the West Coast

Freezing water is often a boater's biggest winter concern, but it's not the only one: Left unchallenged, engine acids, dirt, moisture, microscopic critters and more can conspire against an inactive boat to render it smelly, ugly, and worn before its time. Here’s a guide to preparing your boat against winter's onslaught and making sure it greets next season needing little more than a quick wash/wax and a trouble-free shake-down cruise.

Doing things right is easier when you've got a roadmap to follow, so start your winterization process by making a checklist. The suggestions here can help you create your list, but every boat is different. The best source of information and recommendations for your specific boat will be the owner's manuals for both the boat and the motor. Online owners groups can be useful sources of information too. If you're new to boating, consider enlisting the help of a seasoned friend or hiring a professional.

Change the Oil

If your boat has a four-stroke or diesel engine – whether inboard or outboard – the key winter defence is to change the oil and oil filter at the end of the boating season. This is because not only does the oil itself break down over time, but combustion byproducts accumulate in the oil during use. Normally the oil holds these impurities in suspension and they're not a problem, but over the winter moisture can combine with the combustion byproducts to form acidic compounds that can sit against bearing surfaces and pit them. Change the oil when the engine is warm to ensure the impurities get flushed out with the old oil. Don't forget to change the gear oil, too.

Flush the Cooling System

Regardless of whether your engine has raw-water or fresh-water cooling, if you're hauling out for the winter you need to flush and drain the raw-water side of the cooling system. Your owner's manual is the best source of information for the exact recommended procedures (for outboards and stern drives you'll need a set of water intake "ear muffs"). If your engine has raw-water cooling, run it on the flushing hose for ten minutes (long enough to open the thermostat), and then use a bucket to run antifreeze into the engine to protect the cooling galleries (outboards are typically designed to self-drain, so you may be able to skip this step). If your engine has fresh-water cooling, you only need a short flush cycle, but you must also ensure that the system’s fresh-water side is either drained or has an antifreeze mixture to prevent freezing. Now's also a good time to run in a water-pump lubricant.

Stabilize the Fuel System

Built-in fuel tanks should be kept full over the winter to avoid condensation, which can cause corrosion, contaminate the fuel, and (in diesel-powered boats) provide a breeding ground for "diesel bug" – actually a carbon-eating bacteria that lives in the water layer at the bottom of the tank. If your boat uses portable fuel tanks, another option is to drain the tanks and store them where the temperature won't drop below the dew point.

When you fill up the fuel tanks prior to winter, it's a good idea to add a compatible fuel stabilizer, which helps stop the fuel from oxidizing over time. For diesel engines you'll also want to add a biocide to stop diesel bug (unless you've used a fuel stabilizer with biocide already in it). After adding fuel stabilizer, run the engine for a few minutes to circulate the stabilized fuel into the system. An alternative that some boaters prefer, after adding stabilizer, is to empty the engine's fuel system entirely. On outboards this is easy to do by disconnecting the fuel line and running the engine out of fuel (don’t do it with oil-injected two-strokes, however, or the engine may attempt to run on straight oil after the fuel runs out). For inboards, check your service manual or refer the job to a mechanic.

Fog the Engine Cylinders


Fogging oil is designed to coat the engine cylinders and protect against corrosion. It typically comes in an aerosol and can be sprayed directly into the air intake. Check the product literature carefully to be sure the product is suitable for your particular engine.

Lubricate Linkages

While you're protecting the engine against corrosion, it’s a good idea to clean and lubricate all the linkages and fittings. Refer to your service manual, and use oil, spray-lube, or marine grease as applicable. Some boaters also wipe down the engine's external surfaces with WD-40 or fogging oil to protect against surface corrosion.

Think Zinc

If you boat in saltwater, winter haul-out is a good time to change the zinc anodes protecting the engine, stern drive/prop shaft and propeller. Freshwater boats also have anodes, but typically made of magnesium, not zinc. Don't get them mixed up, or you can set your boat up for serious corrosion issues.

Slacken Drive Belts

To prevent premature aging of the accessory drive belts and reduce stress on the water pump and alternator bearings, some boaters like to slacken the belts off. Put a tag on the engine control panel so you don't forget to tighten them before starting the engine in the spring.

In the Cabin

Inside the boat, the first order of business is to make sure the bilges are dry. Bail or drain them as necessary, and clean up any bilge scum while you're at it (your nostrils will thank you in the spring). Next, drain all the domestic water systems (fresh and black water tanks, water heaters, marine toilet systems and all associated plumbing) and run in a non-toxic RV anti-freeze solution as required.

Keeping interior air dry isn't normally a problem if the temperature is well below freezing, but airborne moisture can wreak havoc onboard when the temperature is hovering just above freezing like it does in the fall and spring (or all winter long in coastal climates). To keep moisture at bay you can use desiccant crystals (calcium chloride), promote air circulation (with solar-powered vents or an electric air warmer, for instance), and perhaps install a dehumidifier if you have power. Also consider a well-fitted boat cover or tarp, which can help stop water from getting into the boat in the first place.

Finally, make sure nothing's put away wet at the end of the season, and if possible take home soft goods (lifejackets, cushions, sails and such) for storage in a dry garage (if that’s not possible, spread them out with air circulation all around). Speaking of sails, avoid leaving them outside on the furler or boom all winter.

In-water Storage

If you're storing your boat in the water, close all sea valves and check that your bilge pump is ready for the winter. This means ensuring the pump intake isn't clogged, checking the flipper switch on the pump is working properly, and ensuring the batteries are fully charged and in good condition.

If there's any chance of the water freezing, you need a de-icing device or bubbling system around your boat, and it's also worth ensuring there's no standing water in the hoses connected to your thru-hulls (drain them or run non-toxic antifreeze into them). Don't think you're immune just because you live on the West Coast - last winter several boats sank in the brackish water of Vancouver's Coal Harbour as a result of freezing conditions bursting hoses that were connected to open thru-hulls.

No Trespassing!

If you're storing your boat on dry ground, it’s a good idea to plug or cover exhaust ports and other openings to prevent rodents from taking up residence. To deter two-legged trespassers, make sure you lock all lockers and hatches before leaving the boat.

Finally, if you can, drop by and visit your boat occasionally during the winter to check that everything is in order and that the boat is sleeping soundly.