Having trouble removing stains...

Hey guys, I need a little help. I did a search on removing stains and most people said to use vinegar and water, muriatic acid, or hot sauce. Well I have some water stains on my board and can't get it off. I've tried vinegar and water and S & N wheel cleaner which had muriatic acid in it and still haven't had any luck. Any suggestions would be great. Its not a big deal if I can't get them off, but I just bought the board off craigslist and would like to remove the stains, so it wouldn't look so crappy. It wouldn't matter if our bindings were in the same spot, but I like mine a little wider than what he rode. Yes I am a Newby & this is a dumb question, but any help would be great. I'm trying to upload a picture but it won't let me.The water stains are brown and are in the shape of the bottom of the bindings.

I finally got the picture to upload. As you can see, the guy that I bought it from never took his bindings off and there is a brown water stain on the board and I cannot get it off. HELP Please!!