One of the first orders of business was to fix the head. I gate valve is used to close the holding tank and divert discharge to the seacock. The gate valve was bronze, and was frozen solid. There was no way to easily remove it without cutting out most of the PVC plumbing. The vented loop was also clogged. I had originally thought to replace the gate valve with a Y valve, but didn't see the value. So instead I replaced it with another gate valve, this time a PVC valve, which will hopefully give better service because it shouldn't corrode. Also, the original gate valve was downward facing and hard to get to through the cabinet door under the sink. Since a new access had been cut though a panel above, I oriented the gate valve differently for easier access.
While that repair got the head working, I also needed a way to empty the tank while at sea. For this I needed to install a Macerator pump, and additional piping and valves. Above you see 2 "Y" valves. Both are meant to be turned together. While in position "A", the head discharge flows into the holding tank, and the macerator pump will empty the tank. In position "B", The head will discharge directly overboard.
The pump itself is located under the port settee (bench). The flexible hose comes from the holding tank in the keel, and the PVC output hose goes to the head, where the discharge throughhole is.
I had to cut a hole to access the tray the PCV pipe runs through in order to glue the fittings on the end. Nothing is simple.