I finally got around to repairing a very small hairline crack in the deck of my 2000 H340. It looked like someone had dropped something on the deck but there was no chipping. The crack was in the middle of the side deck at about three inches in from the toe rail and about one third way back from the bow. The crack was only about an inch long and I would have ignored it except that I saw some tea colored water seep out in the afternoon sun after a day of rain, meaning that the core was getting wet. I called Hunter Marine and they told me that the deck was cored with ½ inch end-grain balsa blocks. I carefully drilled a 3/8” hole into the top skin of the deck in the middle of the crack and was careful not to go deeper than about 3/8" into the core. Using an assortment of dental picks, I removed much of the fibrous core material from an area wider than the hole I had drilled in the deck. The core material did not appear wet but was dark and I assumed that it could have been damp. As I dug down to clean out the material close to the inner fiberglass skin of the deck, my dental probe suddenly dropped about 3” into some unknown space below ($%*&#). Leaving the probe in place, I went below to find the problem. There was a factory installed interior halogen light fixture affixed to the headliner at about the right location and when I dropped the fixture, the dental probe was sticking through the deck coring and headliner. I could clearly see the under surface of the deck coring. To install this light, Hunter Marine had drilled a hole about 1” wide through the headliner and somehow exposed the deck core material above. Looking up from below, I could not identify a layer that corresponded to the lower fiberglass skin of the deck. The wires for the fixture appeared to run out along the under surface of the deck coring. It could have been that there was a much larger hole in the under surface of the deck but I had no way of exploring further. From below, I plugged the small hole made by the dental probe and was able to fully fill the deck hole from above with West System epoxy. The repair seems sound and my next step will be to try to match the color of the non-skid with some gel coat. Given the location of the original crack directly over an unsupported part of the deck, I assume that it was a depression fracture caused when someone walked on the deck. All of the deck surfaces on this boat are otherwise solid with no flexing or hollow sounds. I have other light fixtures elsewhere in similar locations but have not looked underneath. What is holding up my deck from below?
