Transom repair to 23 Sceptre inboard

[gkj]

I just bought a 1977 23 Sceptre inboard with a"punky" transom. The affected area extends from about 10" below the top all the way to the bottom.Moisture readings are high and hammer sounding tells me the plywood core is shot. This is not a load beearing surface like an outboard, and I would like feedback on possible repairs.(drilling,drying and epoxy injection for the short term)and major surgery in the long run if required. Access is limited from the inside because of the liner.Any feedback greatly appreciated,

TNX
BOTES1