Bummer :( It sounds like pie plate access hole time.
I know why it was plugged off now, the fitting is broken off on the bottom of the insulated box, now it just drains into the bilge, now all i have to do is get time enough to replace it.
Ok so where is the hose end that connects to the drain? you may want to plug the end of that hose in the mean time. You don't want a hole at the watering ofcyou boat just plugged with 5200.!