I am a new owner of a 1976 Oday 25. The boat originally had a thru hull head rig and was changed to have a Y valve with a switch to direct the discharge to a holding tank that is stored under the Vee berth. The holding tank hoses were loose and I am re-evaluating and settng up the darn thing. The holding tank has 3 connections. One is large for input (I now made that the 2nd hole from the tank bottom). The 2nd large one connects to a pump out outlet on the topsides of the boat. The 3rd hole is the tiny venting hole that had nothing connecting to it. I just put a gasoline tank checkvalve that permits breathing in and slight breathing out thru this fitting. I have not used the head since setting it up again. I am reading various sources and see that I really should run a vent hose from this tiny outlet to a thru hull fitting installed high above the water line- just below the rub-rail. I am reluctant to jump into cutting a new hole in the hull of the boat. I am interested to learn what other ODAY 25 owners have done to tackle this. What is the thickness of the hull (so I can buy the right size thru-hull vent device)? What type of hole cutting drill bit is recommended? Do I cut an oversize hole and epoxy it with some fiberglass netting then re-cut a hole to house the fitting without a leak? Also I found the Raritan manual that came with the head. It suggests a vented loop between the head and the holding tank. My boat has a loop with a socket to attach a venting hose but no hose is attached. Do I need to connect a hose here and run it to join the vent hose coming up from the holding tank on its way to the thru hull vent fitting? IS the Raritan the original head? I have read on the web that the "joker valve" should be replaced every couple years. Does anyone have experience with this? I have know friends and family with boats with heads who don't recall replacing this valve.