Only self-draining iceboxes drain to:
the bilge. This is less than desirable because it can make your bilge a stinky mess when (not if) something goes south in the ice box. From this, you want the ice box to drain overboard. The bottom of the ice box is below the water line, so you can't have it drain straight to the outside by gravity as your ice box would fill part way with water. From these two points, you must have a pump of some sort to drain the box. Catalina minnimizes through hulls by using the sink drain as the frig drain. I have never traced the line between the pump to the sink drain, but it most likely loops above the waterline some where, and most likely has a vacuum breaker to prevent back siphoning (although the foot pump has a check valve, I wouldn't want to rely on that to keep my vegetables or my beers from floating away on a hard starboard tack). Steve Alchemist C-30T #4764 Alchemist C-320 #909
