M_Boats: M15 Hull Deck Joint

Jerry, Inspecting my M15 at home, I noticed the hull deck joint is very cracked- at least a several foot long crack on each side. I suspect it was from really bad docking (slamming into docks at high speed) or getting crushed between two other boats. The gusts on Saturday were burying my rail, and there was water pooled in the isolated storage compartments on both sides of the cabin. I remember your suggestion about sealing it with flocked cotton and epoxy mix, but how can I get it into the flanged joint? Do you think I need to completely take the deck off so I can clean up the surfaces, or just unbolt the cracked part, pry it open, and inject the mix with a syringe? Thanks, Tyler