Just to share our experience on these;
Shortly after purchasing our 380, I found the galley “thruhull” to be leaking near the base. A quick haul, yard replacement, and $1K later, I realized this might not have been so serious. The PO had serviced the valve and stripped some threads on some of the stainless screws that hold the body together. The thru hull was not leaking, the valve body was. We could have used the plug that comes in the handle to close off the outside opening (from the water), screwed off the body, and screwed on a new one. Lessons – ascertain what is leaking; in my view its very unlikely that its the thru hull. If you take apart a valve to service, be very careful when putting back together.
This past winter I replaced the engine cooling water thru hull and valve – it had been