How to Re-Cover Boat Cushions and Seats (DIY Sewing vs. Upholstery Shop)

Make a list of every cushion and seat, and start with the simplest, least visible one. Photograph each from all sides, including the bottom, the zipper, the seams and any piping. Note which cushions get sat on wet (cockpit, bow, swim platform) and which stay dry (cabin); they need different materials.

• Marine vinyl (PVC, from brands such as Morbern and Sailrite's EverSoft): waterproof, very abrasion-resistant and easy to wipe clean. Sailrite's cautions: it doesn't breathe, so water that gets in through seams is trapped and feeds mildew; water pools on top; and it can get hot in direct sun. Polyurethane faux leather is a softer alternative for shaded areas. Read the product details before you order: Sailrite's listing for Morbern Seabrook, a common seating vinyl, gives a cold-crack rating (how cold it can get before the vinyl cracks when flexed) and notes the fabric has a right and a wrong side. If the boat sits outside in a northern winter, compare cold-crack ratings.
• Solution-dyed acrylic upholstery fabric (Sunbrella and similar): breathes, drains when paired with the right foam, and is cooler on bare skin. Sunbrella says its marine upholstery fabrics resist fading, don't grow mold on the fabric itself, and can be cleaned with bleach without losing color. Use vinyl where people sit in wet swimsuits and want to wipe down, and woven fabric where comfort and breathability matter more, such as cabin or shaded cockpit cushions.

Thread is a small part of the cost but decides when the seams fail. There are two choices:

• UV-resistant bonded polyester (Sailrite recommends Tex 70, or Tex 90 on an industrial machine, in an outdoor grade with UV protection and a non-wicking finish). Cheaper and easy to sew. A thread specialist quoted by Marine Fabricator says polyester's life in the sun is limited and that she would not use it for projects meant to last more than two or three years outdoors; harsh cleaners like bleach also shorten its life.
• PTFE thread (such as Tenara): practically unaffected by UV and cleaning chemicals, and its maker claims it outlasts the fabric. Marine Fabricator puts its price at five to ten times that of polyester, and it is slippery, so it can need tension adjustments. For covers that live in the sun year-round, PTFE is worth the money. For cabin cushions, outdoor polyester is fine. Never use ordinary cotton or all-purpose thread.

Sailrite explains why home machines struggle with marine vinyl: most use drop feed, where only the feed dogs underneath pull the fabric, so thick, sticky vinyl feeds unevenly, stitches wander and needles break. A walking-foot machine moves the top and bottom layers together and takes heavy needles and thread. Light woven upholstery fabric for cabin cushions can often be sewn on a sturdy home machine, as Good Old Boat's writer did; multiple layers of vinyl with piping really need a walking foot. You can rent time on one at some upholstery or canvas shops, or borrow from a sailing club. Fit a new needle sized for your thread before starting.

Unzip or unstaple the old cover and remove the foam. Before cutting any stitching, mark each panel with tape: "top," "front," which cushion, and match marks across every seam (short lines that cross the seam so you can line pieces up again). Then open the seams with a seam ripper. Sailrite's back-to-back seat tutorial does exactly this: separate the old pieces and use them as the pattern. Keep any internal pulls, listing strips and the zipper for reference. On stapled seats, pull every old staple; leftovers tear the new vinyl.

With the cover off, squeeze the foam. Sailrite reuses foam if it is still supportive, dry and free of mildew. If it is crumbling, soaked or smells, replace it now (the seat cushion foam guide covers the types). On stapled seats, check the plywood or plastic base: rotten, soft wood won't hold staples. Good Old Boat recommends exterior plywood sealed with epoxy and stainless or galvanized staples for any new base.

Old covers with pink or rosy stains that won't wash out? Morbern, a major marine vinyl maker, explains that "pink stain" isn't mildew but a dye made by bacteria growing in wet foam, wood or padding, and it works its way out through even well-protected vinyl. A new cover over the same soggy foam or base can stain again, so replace contaminated foam and a damp base, and build the new seat to shed water and dry quickly.

Old covers stretch and shrink, so check each old panel against the foam and the seat before trusting it. Lay each piece flat on paper or pattern plastic, smooth it out, and trace it, transferring the match marks. True up straight lines with a ruler and make left and right pieces mirror each other. Add seam allowance if the old piece was trimmed close; Good Old Boat traced around its cushions with about a 1/2-inch allowance. For simple box cushions you can skip the old cover and trace the foam directly. For curved cockpit cushions, Sailrite patterns the shape straight from the boat's seating area.

Lay the patterns on the fabric with the grain or the vinyl's stretch running the same way on every panel of a cushion, especially on tops and fronts that show. Mark with a pencil or chalk on the back side; pins leave permanent holes in vinyl, so hold patterns down with weights instead. Transfer every match mark with a small notch or line in the seam allowance. Cut the boxing (the strip that wraps the sides) long enough to go all the way around with extra to overlap.

Piping (welting) gives a crisp edge. Good Old Boat cut fabric strips about 4 1/2 inches wide, wrapped them around cord and stitched close to the cord with a cording or zipper foot. Sailrite also sells ready-made vinyl welting. Sew the welting onto the edges of the top and bottom panels first, then add the boxing.

Sailrite's recommendations for outdoor cushions: #5 molded-tooth zipper chain with a matching slider (no need for a finished zipper of a set length), in a UV-resistant brand. Put the zipper where it won't show and where water won't sit on it: along the back boxing, or on the underside as Sailrite does on its curved cockpit cushions. Then plan how water and air get out:

• Vinyl cushions: because vinyl doesn't breathe, Sailrite adds metal vent grommets in the zipper area or a strip of open vinyl mesh in the zipper panel, so air can escape when someone sits down.
• Woven or quick-dry cushions for wet areas: a vinyl mesh bottom panel lets water drain straight through and helps the foam dry.

Use basting tape to hold layers together instead of pins. Stitch around the top panel's welting, add the boxing (matching your marks as you go), insert the zipper panel, then close with the bottom panel. Backstitch at every start and stop. For vinyl cushions, Sailrite suggests a semi flat-felled seam with basting tape to help seal seams against seeping water. Turn the cover right side out and check the fit before going on to the next cushion.

For zippered cushions, Sailrite's trick is to wrap the foam loosely in thin plastic film, put a vacuum hose in the open end, and let the vacuum shrink the foam so it slides into the cover easily. Leave the film in as a moisture barrier with standard high-density foam in vinyl, but remove it with quick-dry foam, which has to drain. For stapled seats, center the cover, staple the middle of each side first, then work out toward the corners, pulling evenly and pleating the corners neatly. Use stainless staples only.

BoatUS's advice for vinyl: rinse and gently wash after every trip with mild boat soap and a soft cloth, never pressure-wash, avoid bleach and high-alcohol cleaners, and use a dedicated vinyl cleaner and protectant when needed. Check your vinyl maker's list of approved cleaners for stubborn stains. Morbern's care sheet is a good example of what to avoid: no abrasive powders or abrasive cleaners, no steel wool, no citrus-based cleaners, no lacquer solvents and never wax on vinyl upholstery, which it says makes vinyl brittle. It also warns that some household cleaners and solvents pull plasticizers out of vinyl, and that dyes from jeans and bright prints can rub off and stain light vinyl. Owners in forums add that "magic eraser" sponges are mildly abrasive and can dull the protective top layer, so treat them as a last resort on a hidden spot, if at all. Cover the seats when the boat isn't in use, with a cover that breathes. For acrylic fabrics, Sailrite suggests restoring water repellency with a fabric protector now and then, kept off zippers.