[drifter]

Not sure if I understand the question/concern as the exhaust ports that go through the hull, at least on my old 1997 31 Open and my current 2003 38 open, were fiber-glassed into the hull during manufacture... They are located on the hull side aft quarter near the stern. They are NOT through the stern.... Not sure where yours are located so can't figure out how re-sealing is required. Aren't they fiber-glassed into the hull?

They are located as you state.  They seem to be held by 3 philips screws but are very solid which is why I am hesitant to try to remove them.