You have to kill the mold before you can remove it so it won't grow back. Try Tilex spray and let sit for a few minutes, then wash off thoroughly with sponge and water. Do small spot first to check for color fastnest.
How Do You Get Black Mold Off Vinyl Boat Seats?
I had a nylon black bag which I had sunscreen in it and the dye from the bag stained our friends boat vinyl seat.. What can we use to get the black stain out?
Try saddle soap that works wonders .
Try some diluted bleach. That's what I found worked best on my wave runner.