First let me say hello to everyone. I have been reading this forum for quite a while prior to buying a "new to me" 1978 Oday 23 this past weekend. The amount of knowledge available on this site is wonderful. I don't know much about the history of this boat, other than it did spend a great deal of its life on a trailer during the winters. It is in wonderful shape for it age. My plans are to take my time and go over it stern to bow, pull all the hardware on deck and epoxy and redrill, check the bulkhead / chainplate for rot, etc. The transom and hull are strong, and I can find no soft spots anywhere. I am stumped on one of the thru hull fittings. I understand the thru hull fittings for the marine head, but there is one on the port side, below the waterline that I am unsure of. It may not even be a thru hull. It looks like it is inline with a ring (transducer?) mounted inside the hull. The part outside the boat looks like a thru hull that allows water to enter while at speed. The marine head and holding tank do not look like they have been used.