Catalina 350 International Association

I have added perhaps 12 oz of coolant over two years (had slight drip from loose hose). Sailing back into port last week suddenly engine overheat alarm sounded. After confirming sea water flowing great in the exhaust, down engine. When cooled down confirmed coolant level very low. Where did it go ??%$#@. When engine was cooled down started it to begin checking things. None in bilge, white smoke not coming out exhaust (perhaps indicating a head gasket or crack), engine running smoothly. I also captured engine exhaust water to look for any sign of coolant, none appeared there. Used an automobile radiator pressure test kit to pressure system to 14 psi- and watched pressure drop pretty fast. Removed zinc from heat exchanger and repressurized system. Should not have had anything coming out thru hole for the zinc but it did, began to flow pretty well, soon flowing with slight tint from coolant color. So, problem found.
Removing heat exchange was not too difficult (thanks to a hair dryer softening the hoses). Bought a replacement from Mr. Cool ($600). Hope this helps someone in the future.