I have a 311 1993 Beneteau. I just removed the toilet raw water supply thruhull fitting because it was loose and leaking. I found that the nut and washer that secures the thruhull was tightened against some sort of inside liner (about .06 thick) which had a gap(about 1/4") between it and the inside of the hull. The Head floor(sole)has a 2" hole cut through to this inner liner. Is this the normal way to install this fitting? When I first saw this setup I thought that the hull was cored. I stuck a tywrap in the gap to see if there was any material between the 2 layers but found nothing. This seems like a strange way to secure this fitting, relying on this weak inner liner for support. Would it be best to cut out this inner liner and tighten the nut and washer directly to the hull? The hull is about 1/4" thick at this point. This seems to me like the best way to go.