If I understand what I'm looking at, that whole set up scares me. I wouldn't mess with it while the boat is in the water
. That plastic thru-hull is way too exposed and could break.
Next time you haul, sooner rather than later, replace the whole thing with a bronze or glass reinforced plastic flanged seacock and thru-hull. It also looks like you have a cored hull
and who ever installed the thru-hull cut away the inner skin and the core
. The whole thing is just mounted to the thin outer skin. That needs to be fixed.