Boat Tarp Guide: How to Cover a Boat for Winter Storage

Boat Tarp Guide: How to Cover a Boat for Winter Storage

A boat stored outside under a loose tarp often comes out in spring with water in the bilge, mildew on the seats and a tarp torn at every grommet. The tarp usually wasn't the problem. The setup was. A boat tarp works when it sits on a support frame so water and snow run off, is big enough to drape well past the rub rail, and is tied to the trailer, not just the boat, with room left for air to move.

This guide covers how to cover a boat with a tarp for winter storage: tarp vs shrink wrap, how to size a boat tarp, how to build a simple support frame, how to tie it down and which tarp grade to choose.

If you're covering firewood or equipment this winter too, see our guide to covering firewood.

Tarp vs shrink wrap vs fitted cover

For many owners, a heavy-duty tarp over a simple frame is the most economical way to store a boat outside year after year.

How to size a boat tarp

Measure over the boat, not just along it:

1. Length: measure from the bow to the stern, including the outboard motor or swim platform, then add enough to drape down at both ends.

2. Width: measure up one side from the tie-down point on the trailer, over the top of your support frame, and down the other side to the same point. That over-the-frame distance is the width you need.

3. Round up. If you fall between sizes, choose the bigger tarp. A tarp that is too small can't reach the trailer and won't shed water away from the hull.

A frame raises the top of the cover, so the width you need over a frame is always more than the boat's beam.

Build a support frame

A tarp lying flat on the boat collects water and snow, sags into the cockpit and eventually tears. A frame gives it a ridge so everything runs off.

• Ridge pole: run a straight board, PVC pipe or adjustable boat-cover pole along the centre line from bow to stern, supported above the windshield and console.

• Cross supports: add bows or cross-pieces every few feet so the tarp can't sag between them.

• Slope: aim for a clear pitch from the centre line down to the sides so rain and snow slide off.

• Pad sharp points: wrap windshield corners, rails, antenna mounts and the motor with foam or old towels so they don't wear through the tarp.

How to tie down a boat tarp

1. Centre the tarp over the frame with the same overhang on both sides and both ends.

2. Tie through the grommets to the trailer frame, not to the hull fittings or rails. The trailer is the solid anchor.

3. Run lines under the trailer from one side to the other, or use ratchet straps over the top, so wind can't lift the edges.

4. Tension evenly. Snug every line, but don't over-tighten a single point; that's how grommets rip out.

5. Leave ventilation gaps. Keep a small opening at the bow and stern, or prop the tarp slightly, so moist air can escape.

6. Check after storms. Clear heavy snow, re-tension loose lines and look for any spot where the tarp is rubbing.

Prepare the boat before you cover it

• Clean and fully dry the boat, including the bilge and storage lockers

• Remove cushions, electronics and anything that holds moisture, where you can

• Follow your engine maker's winterizing steps before covering

• Tilt the trailer slightly or lift the bow so any water that gets in drains toward the transom drain plug

Common mistakes

• No frame. A flat tarp pools water and snow and can collapse into the cockpit.

• Tying to the boat instead of the trailer. Rails and cleats aren't designed for wind load on a tarp.

• A tarp that barely reaches the gunwale. Wind gets underneath and water runs onto the deck.

• No ventilation. A sealed cover traps humidity and leads to mildew.

• A light, low-UV tarp for a full winter. Sun, wind and freezing temperatures break down light tarps fast.

Which BCP tarp for boat storage

BCP makes three tarp grades, all 100% waterproof with grommets for tying down. You can compare them on the BCP tarpaulin page.

For a winter outdoors, choose at least BCP Tarps Super. It adds advanced UV protection, mildew resistance and double-reinforced edges with poly rope inside the hem. For larger boats, exposed lots, heavy snow or high wind, BCP Tarps Heavy Duty is the stronger option, with triple-reinforced edges, closer grommet spacing and the widest temperature range. BCP lists Heavy Duty for industrial, marine and long-term outdoor storage.

The lighter BCP Tarps Standard suits short-term or light-duty covering rather than a full winter on the water's edge.

For more on how tarp materials compare, see our PE vs PVC vs canvas tarps guide.

Frequently asked questions

Can you use a tarp to cover a boat for winter?

Yes. A heavy-duty tarp over a support frame, tied to the trailer and vented at the ends, is a common and reusable way to store a boat outside for winter.

What size tarp do I need for my boat?

Measure the length from bow to stern, including the motor, and the distance over your support frame from the trailer on one side to the trailer on the other. Choose a tarp at least that long and that wide, and round up.

Do you need a frame under a boat tarp?

Yes. Without a frame, water and snow collect on the tarp and it sags into the boat. A ridge pole with cross supports gives the tarp a slope so everything runs off.

Is shrink wrap better than a tarp?

Shrink wrap gives a tight custom fit but is used once and has to be redone every year. A heavy-duty tarp over a frame can be reused for many seasons and adjusted as you need.

How do you keep a boat tarp from blowing off?

Tie it to the trailer frame through every grommet, run lines or straps under the trailer from side to side, and tension them evenly. Check the lines after strong wind.

Get the right tarp for your boat

Before you order, have ready:

• Boat length (bow to stern, including the motor) and beam

• Your over-the-frame width measurement

• Whether the boat is stored on a trailer, on a lift or on stands

• How exposed the storage spot is to wind and snow

Request a boat tarp quote

Send us your measurements, and our team will recommend the right tarp grade and size. Or call 877-540-5678.