need diameter of hole in back of 83 SN

My boat in in storage right now, I have a quick question?

Does anyone know the size of the hole in the back of the boat for the part that you hook to the water hose? Just to elaborate, in the back of my 83 ski nautique, I have a chrome looking plastic piece that connects to a water hose that allows you to run the engine out of water.

Well anyways that piece is broken and I not near my boat, I need to know what size the hole is, so I can buy a thru hull fitting. (i am going to remove that piece and put the thru hull in) I am going install a ballast system and I am going to use that for my overflow hole.

Does anyway know? I would appreciate it.

thanks