heavy hull

I refurbing a 1978 16' cat. It hasn't be sailed since 1988. Hulls are not soft cleaned up pretty well. replaced some part, but while re-gel coating I found one Hull is extremely heavy. When I first got the boat that hull had water, the other dry. Thinking of adding a port to see if extended drying will take care of the weight problem, or do I have some issue not solvable?

Bobb-is,

You are right on track with your thinking. Suspect that the the plastic encapsulation of the flotation foam has deteriorated and the foam is full of water.
I try to keep (known leaking) boat with bows up for several days to drain.
You can stuff the end of your main or jib sheet in the drain plug to wick out the last bits of water (always do this before Winter storage).
Since difference is "extreme", a port added between the pylons is a good idea.
Sounds like you need some significant air movement to dry out.

_________________
1984 H16 "Mister Rogers"
1984 H14 "Sundays"
2000 H20 "Jet"
Sheet In, Max Out