Winterizing a Boat or Camper Before It Goes Into Storage

Nobody winterizes in September. Everybody means to.

The deadline is not a date on the calendar, it is the first night cold enough to freeze the water sitting inside your rig. NOAA’s thirty year averages for Manhattan put the first freeze around October 16 and the first hard freeze around October 25. Those are medians, so half of all years get there sooner, and the night itself does not give much notice.

Most of what goes wrong in storage is not theft or weather damage. It is water left somewhere it could freeze, fuel that sat until it went bad, and a battery nobody thought about until spring. All three are cheap to prevent in an afternoon and expensive to fix in April.

Water is the part that actually breaks things

Water expands when it freezes, and it does not care what it is sitting inside. A cracked engine block or a split water line is the single most expensive thing that happens to a stored boat or camper, and it is entirely preventable.

For a boat, the specifics depend on whether you have an outboard, an inboard, or a sterndrive, so your manual is the authority rather than a blog post. What holds across all of them: get the water out of the engine and the cooling system, and where the manual calls for antifreeze, use it. An outboard left tilted down drains most of the way on its own, which is the easy win people forget. A livewell, a washdown pump, or a freshwater tank has lines too, and they hold enough water to split a fitting.

Then pull the hull drain plug and leave it out. Sitting outdoors all winter, a boat collects rain and snowmelt, and the plug is the difference between that water running out of the transom and sitting in the bilge freezing and thawing until spring. Put the plug somewhere you will find it in April.

For a camper or RV, work through it in this order:

1. Drain the fresh water tank, the gray tank, and the black tank, and dump them before you park it rather than after.
2. Drain the water heater. Turn it off and let it cool first, release the pressure, then pull the drain plug or anode rod. A water heater left full is a common freeze casualty in a camper.
3. Bypass the water heater before you put antifreeze in the lines, or you will fill the whole tank with antifreeze you then have to flush out in the spring.
4. Open the low point drains and let the lines empty, then either blow the lines out with compressed air at low pressure or pump RV antifreeze through until it runs pink at every faucet. Hot and cold, and do not forget the outside shower if you have one.
5. Pour antifreeze down every drain so it sits in the P-traps, and put some in the toilet bowl and the black tank.

Use RV antifreeze, the pink non-toxic kind, not automotive antifreeze. Automotive coolant is poisonous and it does not belong anywhere near a system you will later drink from.

Fuel, and why a full tank beats an empty one

Gasoline goes stale. Ethanol blended gasoline also pulls moisture out of the air, and over a winter that water separates out and settles at the bottom of the tank, which is exactly where the fuel pickup is.

Add a fuel stabilizer, then run the engine for ten or fifteen minutes so the treated fuel actually reaches the carburetor or the injectors. Stabilizer sitting in the tank while untreated fuel sits in the fuel system is a job half done, and it is the most common way people get this wrong.

Leave the tank close to full. An empty tank is mostly air, air carries moisture, and moisture in a fuel system over a Kansas winter means corrosion and a rough start in the spring.

If the oil is anywhere near due, change it now. Used oil carries combustion byproducts you would rather not leave sitting against internal parts for five months.

The battery

A battery that sits all winter and is never charged will usually be dead by spring, and a lead acid battery that has gone flat can freeze, which finishes it off for good.

Take it out and take it home with you. Most winterizing advice tells you to leave a trickle charger on it, which is fine in your own garage and no use at all on a storage lot, where there is no outlet to plug into. So the battery travels: keep it somewhere that does not freeze and top it up every month or so. If you would rather leave it in the rig, disconnect the negative terminal at minimum.

While it is out, clean the terminals and check the water level if it is the kind you can open. Five minutes now saves you buying a new one in April.

Tires, and how it sits for five months

Tires lose pressure standing still, and a tire that sits underinflated in one spot for months can take a set that you feel as a thump for the first few miles. Some of them never come back.

Set the pressure before you park it, and know which number you are setting it to. On a car you use the placard in the door jamb, not the sidewall. On a trailer it is usually the opposite: trailer tires are normally run at the maximum cold pressure stamped on the sidewall, which is a much higher number than anything on your truck.

Two more things people miss on trailers. Grease the wheel bearings before it sits, because bearings that sit wet corrode. And leave it in gear or chocked rather than sitting on the parking brake, since brake shoes can bond to the drum over a long, damp winter.

Sunlight is the other slow problem. Tire sidewalls crack from UV long before the tread wears out, and covers over the tires are cheap.

Cover it, but let it breathe

A cover keeps sun, rain and grit off. A bad cover traps moisture underneath and grows mildew on everything you were trying to protect, which is worse than no cover at all.

Two rules. Support it so water runs off instead of pooling, because a pocket of water freezes into a surprisingly heavy block. And let air move underneath: a breathable cover, or vents cracked open, or both. A plain hardware store tarp does neither. It holds water against the surface and the edges chafe the finish every time the wind blows, and in this part of Kansas the wind always blows.

Inside, prop the fridge door open and leave cabinets and drawers ajar. Sealed up damp is how you come back to a mildew problem.

Mice

Kansas has field mice, field mice want somewhere warm and dry in November, and a parked camper is exactly that. They get into wiring, insulation and upholstery, and the repair is expensive for such a small animal.

Take out every crumb of food, including whatever is at the back of the cabinet you forgot about, and the paper products too, since napkins and toilet paper are nesting material. Then close the ways in. Stuff steel wool into the gaps where plumbing and wiring pass through, and check where the sewer hose and the power cord come in.

People swear by dryer sheets and peppermint oil, and they may help. What definitely helps is leaving nothing worth nesting in and parking on a real surface rather than tall grass.

Then decide where it sits

Once the rig is prepped, where it sits matters less than people assume. A properly winterized boat or camper does fine outdoors on a secure lot, which is the whole point of doing the work above.

The three options, in rough order of protection:

• Open parking. A gated, lit, camera covered lot with a real surface. With a good cover on a properly prepped rig, this is the sensible choice for most people, and it is the easiest to get into on short notice.
• Covered parking. A roof over the top, which knocks down sun, hail and snow load. Worth it if you are keeping the finish showroom clean or you are storing for longer than one season.
• Enclosed. Four walls and a door. The strongest answer for weather and for mice, and the one to ask about if the rig is worth real money.

The thing to sort out before you call is length. Vehicle spaces are sold by length, not by the room sized units you picture for household goods. Measure from the tip of the trailer hitch to the rear bumper, then add a few feet so you are not threading a needle in the dark in January.

What fits where moves around as spaces come and go, and the lots are not all set up the same way. So give us the number and we will tell you what is actually open, rather than you working it out from a page. You can start on our vehicle, RV and boat storage page, or read our rundown of how to pick a space for a boat or camper if you are still deciding.

Before you lock it up

The short version, in the order that works:

1. Drain the water systems, bypass the water heater, and run antifreeze through the lines and traps.
2. Fill the fuel tank, add stabilizer, and run the engine long enough to circulate it.
3. Change the oil if it is close to due.
4. Pull the battery and take it home, or at minimum disconnect the negative terminal.
5. Set tire pressure, grease the trailer bearings, chock the wheels.
6. Clean the inside out completely, food and paper included.
7. Cover it, supported and vented, with the fridge and cabinets propped open.
8. Take a photo of it as you leave it. It settles any question in the spring.

That is an afternoon of work against five months of sitting, and it is the difference between a rig that goes in the water in April and one that goes to the shop first.

If you are not sure what size space you need, call or text and describe what you have. We would rather talk it through than have you show up in November with a trailer that does not fit.

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Written by Thomas Weeks, Director of Operations at Axis Self Storage. Nearly a decade in storage and property management, and the owner you will actually reach.