"Michael Bushey" wrote
My 15 year old boat has black patches on the indoor outdoor carpet. It
appears to be old mildew. Vinegar and baking soda didn't touch it. Carpet
cleaner doesn't work. Any suggestions appreciated.

Chlorine bleach should work, but I'd first try a sodium percarbonate product
like Oxiclean to see if it might remove the stains with fewer undesirable
side effects. Besides the potential for discoloring your carpet, chlorine is
not a good friend to stainless steel and aluminum.