Bildge drain possible leak?

First, thanks for the sight. When I started researching My V20 I was more than suprised to find an entire websight devoted to it! I have a 1972 20' w/ a '79 merc 150 with about 5 hours on the rebuilt motor. I will get some pictures up soon enough. I have taken in small amounts of water sitting out on Lake Erie. I noticed the actual sleeve the bildge plug goes into has a small gap and the collar does not actually sit fluch aginst the boat. It's the same style as Drgn3's drain.
Can I just put some 5200 behind the collar and gently tap a 2x4 with a mallet to drive her home?
My old man tells me not to worry about it, and it seems every boat magically takes on some water, but it has become a mission.
Plus i didn't wire in the bildge pump yet (I know I know)
Also a small gouge in the gelcoat below the water line. Fiberglass not damaged, but a small chunk of gel is missing.....Will water creep through undamaged glass? Should I treat the gel repair as neccessary and not just a cosmetic flaw?