I searched the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly scarce B4 1840, rare B4 1800. There is AT LEAST a 35% chance your ancestor's rcds aren't in this database.
For the McWhorter surname (+variants) in all Ireland, there are 228 B rcds dating from 1721 and 363 M rcds dating from 1813. The majority of these rcds are in the counties of Antrim, Armagh, and Down. This suggests a Scots-Irish origin for the surname.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.