Having written about keeping water out of cored decks it is interesting to enclose this picture of a boat that I surveyed for a friend today. Here is a classic case of water intrusion into the core through deck fittings. Although you can't see it in the photo the water deck fill was leaking badly, the bedding had long since broken down and this has allowed water into the balsa, the readings on the moisture meter was off the scale. To make matters worse the strain on the guard rail from the wires and crew leaning against them rocked the base back and forth cracking the gelcoat allowing even more water to penetrate, all in all bad news. Water finding it's way into the core freezes in really cold weather, expands and then allows room for even more water to migrate farther into the core. Up here in the northeast USA these freeze thaw cycles are not uncommon but can happen in almost all parts of the country at some time or another.
The deck on this boat was starting to show signs of serious delamination and this was likely to result in a hefty repair bill. All could have been prevented by not letting water get into the core in the first place. If you have deck fills and other deck penetrations then it is good practice to lift them every few years, scrap away the old sealant and replace it with some fresh bedding compound.