Seal and cover it
Once dry, you can apply a protectant to lock in the finish. A sealant will also help keep future stains from forming or make them easier to clean. Lots of protectant sprays are available from Meguiar, 3M, Starbrite, Marine 31, or 303. Don’t use automotive or household/patio cleaners/protectants that have silicone in them.
Be sure to cover your Bayliner for storage because sun damage on vinyl is almost impossible to clean or reverse. However, be sure to provide good ventilation under the cover because dark, airless environments are havens for mildew that looks like a pink stain on white vinyl (which is why it’s called “pinking”).