I have a 1976 O'day 25 I just purchased. The cooler built into the Galley has a strange plug in the bottom. It is hollow in the center yet does not drain. I cannot determine how to remove it. It has slots in a plus sign configuration. I tried using a large coin like device to unscrew it. It only unscrews 1/4 of a turn and that does not enable any drainage at all. The prior owner never used this built in ice box. Any advice on how to remove this plus would be greatly appreciated. Also, under the ice box is a hose that connects in a Y manner to a hose coming down under the sink. The unified hose that results goes down to a thru hull valve that has a traditional backyard spigot handle. After shooting some WD40 on it, the handle turns easily around 25% of a turn yet this does not open the thru hup=ll fitting to enable any water to pass thru it. I checked it out when the boat on blocks out of the water. I forgot to push a coat hanger up the thru hull fitting to see if anything was clogging. Any advice here is also appreciated