blotchy staining

[agriman]

I have a yellowish stain on the swim platform when wet. After drying the sun will bleach it out. I use Clorox bleach for cleaning. It appears quite blotchy. A fiberglass guy says he has never seen it before. Any ideas of whats causing this?

 

[PascalG]

Did somebody sit on the platform with some bronzer ? Some of them contains pigments that stains vinyl and fiberglass. Goes way a with time

 

[Phillbo]

Is it near your fuel cap? I've had some splash back when fueling and it will leave a yellow stain that goes away when exposed to the sun.

 

[agriman]

No, to both reply's. I'm begging to think I could have moisture under the gel coat. Also 4 years ago I had the surface re-done and davit holes and O.B. motor holes filled in. The stain started to show up this season.