Use SoftscurbTM. Works magic on gel coat stains and won't harm the gelcoat. Use a microfiber rag and apply a little dab on the stain and do a little finger swirl too remove. Just before it is dry, buff out with a clean microfiber rag.
When you get the Softscrub, get the lemon scented stuff and not the bleach one. The bleach can stain your clothes or irritate your hands if gets on you. Since the bleach really doesn't help with the stain on the gelcoat, there is no need for it.
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