Are these bronze throughhulls? With proper seacocks on them? Or ball or gate valves?
It is possible someone did pour lead/solder into them to make a permanent seal, or used some kind of epoxy
compound. I think you'd want to take a gouge and dig some out from the outside, to see what it is. If it IS lead/solder...that blueish discoloration could be heat damage from someone's torch. At that point it becomes easier to replace than to start spending time investigating what it might be and what damage there might be.
Depending on how the throughhulls were installed, they can be easy or difficult to remove. If they were bedded with 5200 or another "permanent" adhesive
, sometimes you need to unplg them, then cut them laterally with a Sawzall (or hand blade) and "implode" them into the hole to get them off the hull
. If they were put in with a proper bedding compound, you should be able to put a water pump pliers or other large grip on the interior
hex nut, stick a "pickle fork" into the fitting (there's a bar across the middle of it, or was, before it was plugged) and unscrew it from the hull.
No easy way to be sure.
Exploring your options in the water doesn't have to be frightening. Damage control plugs work--especially if tapped in from the outside. And, a large ball of cheap
beeswax (toilet bowl seating ring) will plug them very nicely, too. From the outside.
Overall, replacing it probably is the most reliable and expedient option. If you find a nearby yard with a lift
, you can often get a break on just an overnight lift--they haul you, back up, and leave it in the sling overnight. You work fast before sunset and they launch it again in the morning, and charge you less because it was just up-and-down without having to stow the boat someplace. Or course, you still should have two people (one inside one outside) and tools of destruction in case it just won't go.