Boat cushions are a prime breeding ground for mold and mildew. With plenty of dark, damp and warm surfaces on which to flourish, it is common to find colonies of mold growing happily on your boat cushions. Boat cushions are usually made with mold-resistant fabric, but mold can still grow on any dirt or debris on the cushion, particularly on the seam and edging grooves. Removing the mold is easy; removing the remaining stain is difficult.
Remove the cushions from the boat. Use a stiff-bristle brush to remove the surface mold growth. If the boat is in a garage, take the cushions outdoors when brushing them to avoid releasing mold spores into the garage.
Test a hidden area of the cushions to check for colorfastness before trying any of the cleaning methods. Before using the lemon juice, powdered bleach or chlorine bleach, apply a small amount of the solution to a hidden area of the cushion. Wait 15 minutes to see if the fabric changes color. If the fabric changes color, choose a different cleaning solution. Most boat cushions are made with colorfast fabric, but it is better to check first.
Make a paste of 1 tsp. lemon juice and salt. Apply the paste to the mold stain, and set the cushion in the sun. Rinse the cushion with cool water after the paste has dried.
Mix 2 tbsp. of powdered bleach (containing sodium perbolate or potassium monopersulfate) with 1 pt. of hot water. Sponge the solution on the mold stain, and let it sit for 30 minutes. Rinse the cushion with cool water.
Use liquid chlorine bleach for tough mold stains. Mix 2 tbsp. chlorine bleach with 1 qt. of warm water. Sponge the solution on the mold stain, and let it sit for 15 minutes. Rinse the cushion with cool water. Use a clean sponge to apply white vinegar to the area to neutralize the chlorine bleach. Rinse again with cool water.