Hi David
To date, only the county-based genealogy centres in Ireland have attempted any large scale, systematic indexing of church registers in their localities, and these can be searched at
https://www.rootsireland.ie/ . For example, the County Mayo database, compiled by North Mayo Heritage Centre and South Mayo Family Research Centre, contains pre-1900 registers of 55 Roman Catholic parishes, 23 Church of Ireland parishes and 9 Presbyterian congregations.
As each county-based genealogy centre, whose records are accessible at
https://www.rootsireland.ie/, employs a genealogist, with knowledge of both family history sources and local history, it makes sense to contact them to see if they can assist you; for example, to answer queries you may have about place names, surname origins, sources to search, record offices to visit, or research recommendations.
Contact details for North Mayo Heritage Centre and South Mayo Family Research Centre can be found at
http://www.rootsireland.ie/mayo-genealogy