Just curious if anyone else has a black tar epoxy layer between the glass and gelcoat on their hull. I have a 1979 299 that always gets some blisters, but they have almost always stopped at a black layer under the gelcoat. Since the blisters did not penetrate the glass, I just clean then fill with West System and move on. I never new what the black layer was until just recently, when someone at the boat yard recognized it. Now it all makes sense. Was this something a previous owner did, or was this something that was done at the factory?