We just cleaned today using Awesome from the store and a soft brush but it does seem like the steamer would make things easier.
Best pontoon vinyl cleaner. Just be careful using on vinyl and make sure you use a protectant after cleanings to keep the vinyl from drying and cracking. In like manner Handheld or canister-style with a variety of separable wands and hoses are better for little tight upholstery surfaces. Make a solution of 1 gallon of water and 14 cup of mild soap.
Sunscreen is the killer of pontoon seats. I recommend using a green scrubby pad like you scrub pans and dishes with to clean with instead of paper towels. Id start with that first before trying anything more harsh or the traditional chemical vinyl cleaners.
Lightly apply Wise Vinyl Cleaner directly on the vinyl or leather surface and wipe off completely with a clean microfiber cloth. I use a soft rag or sponge and that combination has worked on every stain Ive encountered. Our Boat Care Products will help you.
I also like the Mr. Stock your first-aid kit with alcohol wipes that you can grab for quick spot cleaning. One of the best ways to prevent mold and mildew from appearing on your vinyl seats is to keep up with a regular boat maintenance schedule.
If you want a product to use without the need for scrubbing and scraping this JJVs Best ALU100-G Aluminum Cleaner will likely a great fit. What type of cleaner to get vinyl pontoon seats clean. We have a 2013 22 SFFX with the vinyl decking.
Take precautions and do not spray Oxi-Clean into the water. Or apply Wise Vinyl Cleaner to a clean but damp microfiber cloth and wipe the vinyl or leather surface in one motion. The best rule of thumb for cleaning pontoon furniture is to use mild soap and water or mild cleaning products such as Fantastik or Formula 409 for tough stains.