Vinyl upholstery that sits in the sun for long periods, like the vinyl seating on a boat, will eventually require some attention. Vinyl conditioners can help prevent the cracking of the vinyl, but if you have seats that are already starting to look a little brittle, or if the vinyl has already begun to crack, a simple repair will add years to their life and save the cost and effort involved in replacing the seat covers.
Clean and prepare the surface. Usually, this is nothing more than a wet wipe-down with water and a mild detergent to remove any oil on the surface of the vinyl. Be sure the surface is completely dry before continuing with the repair.
Apply the repair compound using the applicator supplied with the vinyl repair kit and spread with a plastic knife. Plastic utensils are available from most grocery stores, are inexpensive and won't absorb the vinyl repair material.
Allow the repair compound to cure completely. Smooth out the repair with 600-grit sandpaper.
Make color matching or color changes by using a vinyl spray paint, which can be found at most auto parts stores. Two light coats should be sufficient; if you match the original color, the finished product is less likely to show scratches that occur in the future.
Apply a vinyl conditioner to the repair to help prevent future cracking. This step is particularly important if your boat has an open cockpit where the vinyl is exposed to direct sun for extended periods. Apply the conditioner to all exposed vinyl surfaces.