I may have found another likely candidate for John Coulter. I would think whoever did the pedigree on familysearch.org was from the USA. So I think I need to keep checking that angle.
Anyway, I have found a Coulter family in all of the Census in Wayne, Washington Co., Wisconsin. John (Jan 1825(Ire) - Jan 24, 1902) and wife Sarah (Feb 1830 (Ire) - Jan 7, 1905) said to have both emigrated in 1845 and first daughter Sarah born in NY. All the rest of the children were born in Wisconsin. They are: MARY, JOHN, Jane, James, Eliza, Wm., Thos, David. The 1900 Census says there were 11 children and 6 then living at that point. The Parents lived into their 70s.
There is also another Coulter (Colter, Culter, Calter, Culton) living on the farm next to them - He is Wm Coulter and he is basically 12 years older than John Coulter. He has a larger family with him in the 1860 Census - ALL born in Ireland. But by the 1870 Census - he is living by himself - age 57. Can't figure that out.
Anyway, if these turn out to be yours - you will be delighted to hear there are tons of Coulters still in the area for you to ring up.