How do you determine which size -AN fittings you need?
 

I need to relocate the water pickup at the back of the boat and so I need a longer braided 3/4 hose but I'm not sure what the -AN fittings really are. Do you measure from the outside (they are 1" wrench size on the outside, the inside thread (which looks like 7/8) or the hose size 3/4?

I am pretty sure they are based off the hose size. 3/4 should be a -12?

Good link Paul, it looks like it might actually be 5/8 hose, it's hard to tell with the braided covering. The 1" nut size and the actual adapter identifications show it as a -10AN connector.

Then it is 5/8.

Make the fraction a base of 16, and the top number is your AN size.