Boat seat covers can protect your boat's original seat cushions from severe fading from the sun as well as wear and tear from normal use. Boat seat covers can allow you to change the look of your boat seats to any colour or pattern that's available in durable, waterproof or water-resistant material. Sewing your own simple boat seat covers is usually more economical than having them custom made, just make sure to use marine-grade material.
Measure the length, width and depth of the boat seat cushion.
Calculate the length and width of the material you will need to cut for a rectangular boat seat cushion by dividing the depth by 2 and adding the result to the length and width from Step 1. Add 2.5 cm (1 inch) to the length and width for the seam allowances.
Measure and cut two rectangular pieces of material for each boat seat cushion.
Place the wrong sides of the fabric together and pin along the two long sides and one short side. Leave one short side open.
Sew the three pinned sides together, using a 1.2 cm (1/2 inch) seam allowance.
Pin either a zip or a Velcro closure to the open side.
Sew the zip or Velcro closure to the boat seat cushion cover.
Remove the pins and turn the boat seat cover right-side out.
Place the boat seat cushion into the cover and zip or Velcro it closed.
If you are using striped or patterned fabric, you may want to match the stripes or the patterns on the covers' seams. Pay attention when you mark and cut the fabric so you can plan for the pattern, remembering to allow for a 1.2 cm (1/2 inch) seam allowance. Spray the new seat covers with a fabric waterproof protectant and a mildew inhibitor spray to make them more durable.
Don't forget to use a heavyweight or upholstery needle in your sewing machine. Standard needles can break when stitching through thicker materials. Use a zip intended for outdoor marine use.