So the good news is that the patch appears to be watertight for now if there is water held in the pipe itself.
The bad news is that you don't know what material has been used to seal it, or how robust the patch will be. Most skin fittings I've seen are mushroom-headed on the outside of the hull. Is there evidence of the mushroom showing on the hull, or is the repair flush with the rest of the hull? A picture posted up here will help.
Personally, it feels to me that glassing over a skin fitting is a bodge. You have no way of knowing how long it will remain watertight, and the last thing you need is for the patch to delaminate and leak at sea. With the pipe still in place if/when the patch fails it could fail catastrophically.
The correct way would be to remove the skin fitting itself, then feather the edges of the existing fibreglass back and glass over the hole inside and out, before sanding down and applying gelcoat. I'm no expert on glass repairs though, so hopefully someone more knowledgeable will be along soon.
Might be worth sanding back the hull patch to understand how the pipe has been sealed. Best case would be that there's a bronze plug in the end of the pipe. Worst case could be newspaper and anti-foul...