How to clean off dark marks on gelcoat?

[bobholiday]

Richard's recent pressure wash post got me thinking... my Centaur is getting more and more dark marks on the gelcoat from my feet. I wipe at them with a damp cloth, but it seems to have soaked in. What's the best thing to use to get this off?

[Dickh]

Try a mild kitchen cleaner, or if really stubborn an abrasive cleaner line CIF or similar. Then polish. I use the Ecover Multi Surface cleaner which is good.