Any details on the sources for the RC parish of Skibereen that I can locate
(*) all give the same details - i.e. earliest available records are Baptism records are from 1814, marriages from 1837.
* National Library RC parish details, Irish Times RC record sources, Ryan's Irish Records etc
Few rural RC parishes have records before about 1830.
Sometimes you can try searching adjoining parishes for details in case the families lived near the boundary of the parish, but in this instance none of the neighbouring parishes have any earlier records. You can see a map of the West Cork parishes on the Irish Times website - see :
RC Parishes West Co.Cork (click on the parishes on the map to see details of dates available)
Unfortunately it seems that most Church of Ireland records for the parish of Creagh, which contains Skibbereen, have been lost - probably during the civil war.
Shane