Yes, under the galley sink. I have two different sizes there.
The larger one I would like to order.
It's for the raw water intake.
In 1988 EY put the engine intake sea cock under our galley sink. Then they had to bore several holes in our partial TAFG to route the hose (rather laboriously) back to an exit point in the molded bed log on the port side below the pump. Perhaps someone was obsessed with putting the engine water intake in that area on all EY boats?
Anyhow, I moved it back under the front of the aft cabin berth, where there was also decent room for a Groco strainer. The hose goes up that port side of the engine compartment and makes a pretty straight path to the pump.
The only thru hull fitting under our galley sink since then is the drain hose. Per good advice here, it gets replaced about every 5 years. :0
And yes that valve is closed any time we are off the boat.
I would guess that these smaller thru hull fittings are 3/4".