How to Fit, Support, Clean and Store a Boat Cover

If you're buying, measure the boat yourself: centerline length from the tip of the bow to the farthest point you want covered, and maximum beam. BoatUS reminds owners to account for bow rails, trolling motors, consoles, windshields and swim platforms. On a cover you already own, look for baggy areas, straps that won't reach, and spots where the fabric is stretched tight over a sharp edge.

Mercury advises letting the boat dry and air out before you put the cover on, because mold and mildew thrive in damp, dark spaces. Brush leaves and dirt off the cover too, so they don't fall into the boat when you roll it on or off.

Corners of the windshield, bow rail ends, rod holders, antenna bases and cleats all wear holes through fabric. The BoatUS Foundation found that new wear points showed up as covers settled over the winter. Pad them with pool noodles, foam or old towels, and check them again after a few weeks.

Water must always have a slope to run down and off the sides. Put support poles or a support system in the low areas (usually the cockpit and the stern). Pad the top and bottom of each pole so it doesn't punch through the cover or mar the deck, and put a non-skid pad under the foot so it can't slide. The BoatUS Foundation found that the poles included with many covers weren't strong enough on their own; they added extra strapping and poles and still saw poles break under pooled water. Plan for more support than you think.

Start at the bow, roll the cover aft, and pull out wrinkles and low spots by cinching the side straps evenly. Don't overtighten one side; that pulls seams. Make sure straps are long enough to reach the trailer or a secure point. On a boat on stands, run straps under the hull to each other, never to the stands. A BoatUS editor who fought a complicated full cover for hours learned a few shortcuts: start any zipper a few inches first, then do the snaps, then finish the zip; pull an extra foot or so of slack through ratchet straps before you start; and work all the way around the edge before you go inside and set the support poles, adjusting them last for a tight, tent-like shape.

Use the cover's built-in vents and keep them open. A tight cover with no airflow traps moisture and grows mildew. If your cover has no vents, prop it so air can move under it at the ends.

Only trailer with a cover made for it, with all tie-downs fastened so no loose fabric can billow. Stop and check the straps after the first few miles. Keep loose ends tucked so they can't whip the paint or wrap around a wheel. Never trailer with a mooring or storage-only cover, or with a tarp. BoatUS notes that most trailerable cover makers want the straps buckled to the trailer frame (you can preset the buckle lengths), that every strap point along the cover should be used at highway speed, and that storage support poles shouldn't stay in while towing because they tend to work free and leave the cover loose.

The BoatUS Foundation recommends checking a covered boat at least once a month and after heavy rain or snow, and removing any pooled water or snow. During their test, most covers needed to be bailed out after storms. Gently push water off from underneath with a broom handle, never by climbing on the boat.

Brush or blow off leaves and bird droppings, then rinse with a gentle hose. Wash with mild soap and a soft brush or sponge, and rinse well. Skip pressure washers (Yamaha warns they damage the fabric), washing machines and dryers. Some makers advise against any brush at all, so check your care label. Let the cover air-dry completely.

Mildew grows on the dirt, pollen and moisture sitting on fabric. For acrylic canvas, Sunbrella publishes a diluted bleach and mild soap recipe for mildew spots, used sparingly and rinsed very well, away from the water. Polyester and coated fabrics may need a different product, and some cover makers say not to use bleach at all. Use the cleaner your cover maker names, and test on a hidden spot first.

When water stops beading and starts soaking in, the factory water repellent has worn off (deep cleaning speeds this up). On a clean, completely dry cover, spray a re-treatment product approved by your cover maker in thin, even coats on a calm, dry day, and let it cure as the label says. BoatUS adds some specifics for acrylic canvas: skip silicone waterproofers (they don't bond evenly over the factory fluorocarbon finish), and pick a fluoropolymer-type product instead. Solvent-based re-treatments can damage clear plastic windows and plastic zippers, so cover or remove them, keep overspray off gelcoat and walkways (it makes them slippery), spot-test for color change, and spray two light coats at right angles to each other. Acrylic canvas in daily use often needs this after a few seasons; confirm with your fabric maker.

Thread usually fails before fabric. BoatUS says fraying stitching is often the first thing to go on a fitted cover. Have loose seams restitched while they're short, and patch small holes with a repair kit made for your fabric. Replace broken buckles and torn tie-down loops before they let the cover loose in wind. Snaps torn out of the fabric are a common problem on snap-on covers: iron-on patches don't stick to acrylic canvas, so the usual fix is a canvas shop sewing a reinforcing strip along the edge and setting new snaps, or new snaps placed a little away from the torn holes. To keep the rest from pulling out, lubricate stiff snaps with a snap or zipper lubricant, and fit the cover on a warm day when the fabric isn't shrunk tight; pull on the snap, not the fabric, when you unsnap it.

Never put a cover away wet. Yamaha's method: fold it lengthwise into thirds or quarters, edges toward the middle, then roll it from stern to bow. Store it in a breathable bag, off the floor, in a dry place away from rodents. Label the bow, stern and centerline with a marker so next season's install is quicker.