Cleaning boat seats is not easy. Nothing is worse than dirty seats. Those black dots and blobs look unsightly, cause the crew to stand instead of sit, and cause your boat to diminish in value.

Unfortunately, making mildew-stained vinyl look like new proves nearly impossible — and in many ways, it’s a unwinnable battle.

Mildew is a fungus

You can clean it off the vinyl’s surface and kill the spores with a disinfectant, but unless you replace the seat’s foam as well as the vinyl covering, it will come back. You’ll get one season, maybe two depending on humidity and temperature, but just cleaning the stains off boat stains won’t end your mildew problem.

There’s no definite answer to the best mildew remover for boat seats. Many try cleaning with a 50/50 mix of white vinegar and water. But virtually every vinyl manufacturer cautions against using harsh chemicals like bleach, which may damage both the vinyl and the thread stitching it together.

Another approach to cleaning boat seats

You also can find replacements at an online upholstery shop that has your boat pre-patterned. A surprising number of boat cushions are available on eBay or Amazon. The more common remedy involves hiring a local upholstery shop (or shipping the cushions to one if there aren’t any in your area) to make what you need.

Look for a replacement material that has an anti-fungal or anti-­microbial treatment. Ideally, it should meet American Society for Testing and Materials G21 standards, which rate the resistance of synthetic polymeric materials to fungi.