Can someone please tell me if a 1975 Hobie 16 has a foam core or a balsa core?

What is the primary reason for this delamination? Is it balsa rot, or simply the result of sun and heat over years of age finally just giving up the bond? I realize the 1970's fiberglass technology was in its early stages.

I discovered that my delamination is large. It is about 2/3 the length between the front pylon to the tip. The total length is more than 3 feet!

I drilled several holes through and along the centerline in about the center of the delamination the core has settled fairly low. Can or should I attempt to pull up this core? I thought I might be able to do this as I mistakenly drilled all the way through (Opps!) in a few places. I thought I might be able to tie say some strong fish line around the center of a tooth pick or other small diameter dowl. If I push this all the way through I hypothesized that the toothpick would dangle and when pulling on the fish line it would cross the hole and allow some uplift. If I did this and put say 2 or 3 of these in a couple of places and held the tension, I could lift up the bottom layer. Thus when comencing with the repair of injecting the epoxy, it would require much less epoxy which I believe would also result in a stonger more long lasting repair. After the repair I could just cut the fish line and sand off.

What's the consensus of opinions on this?

Final question. After I do this repair, what kind of life will this boat have? What I'm really asking, due to the extent of this delamination and the boats age, should I just sell the boat next year as it's on its last legs, or will this repair last me say 5 or 6 years of family day sailing (no racing)?