Thru-hull questions

[dbetterred]

My 1984 v20 has 2 below water line thru-hulls on each side. One is for the cockpit drain and the other is for the in floor fishbox overflow. the fishbox thru-hull is one size smaller than the floor drain. Do you guys know what size fittings they are? I was thinking 3/4 or 1 inch for the fishbox and 1 or 1 1/8 inch for the floor.
I don't want to order the wrong size and be screwed, I'm already behind schedule for the first launch!
Are the thru-hulls size determined by inside diameter, like hose? Or by the size of the hose that fits the fitting?

Thanks in advance!