I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For John Loughran M 1874 +/- 1 yr somewhere in Ireland, I found 10 rcds: 1873 Antrim, 3-1874 Armagh, 1874 Down, 1875 Antrim, 3-1875 Armagh, and 1875 Down.
For Ann Kinny M ditto, I found 2 rcds in 1874 Roscommon: 1-civil, 1-church. These are likely duplicates. Neither matches any of the rcds for John. Suggest you visit the database and use an expanded search range for their marriage.
You didn't state whether any children were born in Ireland. If so, this is valuable info - much easier to search for offspring.
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.