I have a used board that has seen a few good years of surfing and the deck appears to have sunk sufficiently that the fcs plugs are now higher than the glass. On the left side there are circular cracks around the plug and it is apparent that the board is taking on water. Any ideas how to approach repairing this? My goal is to fix it sufficiently that I can put a pad over it afterward to prevent it the deck from sinking again in the future.
If the foam under the cracks are already brown-ing, you should route out the crack, fill with resin/micro ballon mix, and cap the whole menagerie with two layers of fiberglass, to give it structural integrity and water seal.
If you don’t have a router, use a drill, tape off the bit to 1" depth, and clean out the crack.
When we get a board with cracks in it like you described we usually treat it like a ding repair. We grind down the plugs flush, reglass, do a cheater coat, and polish.