I HIGHLY recommend trying to force the Skeleton Galleons to crash into the rocks to damage and sink them if you are trying this event on a sloop. Being out gunned is hard enough, so using the area to your advantage will help a lot.
Another tactic is to Keg the galleons. Dropping a lit Keg below deck will wipe out any skeleton that can make repairs and deal tons of damage. I’ve sunken several Skeleton Galleons using this method while sailing solo.