Under your kitchen sink, do you have a can of Comet, or Ajax, or Barkeepers Friend, or some other cleanser? If so, take it, a small towel and a bowl of water out to the boat-- wet the rag, and shake enough cleanser on to make a little mud. Now rub a 6" square area hard for about 15 seconds--
If it doesn't help, or you can feel the slivers of the metalflake in the rag, it's too far gone for polsihing--
But if you get a shine, then all you need to do is get some rubbing compound, or just keep using the cleanser, and keep polishing.
FWIW, I rub out my gelcoat with liquid BarKeepers Friend... works just as good as any polish or compound and it's less than $3 a bottle.
I follow up with Dri Wash-n-guard. No silicone or wax ever touches my gelcoat.