I search the IFHF's online database @ ROOTSIRELAND.IE. It has abt 19 million B/M/D and other records for MOST Irish counties. Records before 1863 are increasingly sparse and al most non-existant prior to 1800. Many early B/M/D events weren't recorded, or the records didn't survive.
For Pat(rick) McCann B 1825 +/- 20 yrs, somewhere in Ireland, with a father forenamed John, and mother Cat(herine) Blair, I found 0 records.
For a John McCann and Cat(herine) Blair marriage 1815 +/- 20 yrs, somewhere in Ireland, with the parents' names unknown, I found 0 records.
Sorry for the unsupportive news. Hope this helps. Good luck and merry Xmas.