Transom repair

[Joker2]

I just got a 1975 V20,( no motor ) need to repair transom before I put a motor on it I was thinking about hogging out the wood a nd filling with arjay or nidecore untill I realized two big vertical cracks on the inner skin right under where the motor would be, just above where the deck meets the transom. I feel like maybe the stringers are not attached, not sure
I will send pictures, this could be a nightmare.I am trying to avoid ripping the whole back of the boat off. Is there another way to tell if the stringers are good?