This is from the MasterCraft owner's manual.
While the vinyl is made to withstand the elements, it is important to care for vinyl by keeping it clean at all times. Many substances may stain the vinyl if left untreated over a period of time. Remember to remove any contaminant and clean vinyl immediately.
Regular washing with mild detergent (see attached information) and warm water or vinyl cleaners is sufficient to keep the cushion and vinyl coverings in good condition. Do not soak the cushion, and dry thoroughly after washing to prevent mildew accumulations when the boat is covered. Spray the cushions with a mildew repellent and prop them up in the boat when it is covered to take advantage of air circulation.
MasterCraft vinyl is made to withstand the effects of sun, heat, acid rain and soiling, under normal conditions, but this does not preclude the cleaning requirements. Please consult the following cleaning recommendations before cleaning your upholstery.
Certain household cleaners, powdered abrasives, steel wool, and industrial cleaners may cause damage and discoloration, and are not recommended for use. Dry cleaning fluids and lacquer solvents should not be used as they will remove the printed pattern and gloss. Waxes are not recommended, as many contain dyes and solvents that can permanently damage the vinyl’s protective coating.
In some instances, consumers have reported the appearance of a pink stain on vinyl that is resistant to various cleaning methods. Although there can be other causes for pink staining in vinyls, most pink stains are caused by dyes produced by micro-organisms. These dyes are metabolic products of the micro-organisms, otherwise known as a form of fungi.
It is virtually impossible for consumers to avoid these micro-organisms as they exist in the atmosphere, which are more prevalent in high-humidity areas. Rain cleanses the air, with the result being that the micro-organisms are deposited on items such as marine vinyl.
While the vinyl is treated to resist the growth of micro-organisms (meaning the vinyl is not a food source), the stain results from failure to properly clean and maintain the vinyl. This means that after use, the upholstery must be cleaned with a soft brush and warm soapy water, followed by a thorough rinse with clean water.
This situation is worsened if the boat is stored without proper ventilation or if the boat cover is put on while the vinyl is still wet, creating a situation in which all forms of fungi (mold and mildew) thrive.
Failure to follow these instructions in the proper care of upholstery may cause your warranty to be voided!
The cleaning table presented in this section is offered only as a suggestion and as an aid in attempting to deal with stains. We do not guarantee that the cleaning methods will work. Stains from any external source are unlikely to be covered by warranty.
All of the products listed as recommended are especially good for routine care. Subsequent to publication we have been advised that 303 Fabric/Vinyl Cleaner(TM) is, followed up by 303 High Tech Fabric Guard(TM), highly recommended as a result of testing by the upholstery manufacturer.