I don’t have a 26, but I did replace the stern tube hose on my O’Day 322. I think mine was 2” ID for the hose (so about 2” OD on the stern tube. Mine was a little loose, but the stuffing box is 2” OD, so that is what I went with.
I contemplated putting a few wraps of fiberglass and epoxy to build up the stern tube diameter if it was too loose, but did not end up needing to do that.
Hate to say it, it you are better off getting out to the boat abs measuring both the stern tube OD and the stuffing box OD (make sure they are the same).
What size prop shaft do you have? Not sure if that helps determine the stuffing box size, which determines the hose size. For what it is worth, my shaft is 1”.
Good luck....aren’t boat projects fun
Greg