As you may know most of Irelands records were destroyed in a fire in the fourcourts in 1922. This means that all the census and other records no longer exsist. Only parish records that were kept in local churchs survived. Most catholic parishes started keeping birth and marriage records from around 1820 onwards (some as late as 1830). However in an area that was predominately protestant the records started around 1800 or 1790. You're one of the lucky ones if you can trace your ancestors back further than 1800.
The only suggestion I can make is to look at the hearth rolls and house books but I dont know if these are online or not.
I wish you well in your search, but I don't really know how much farther you can go back. Have you any idea what he did for a living? Maybe he is listed in Estate books or if he was protestant he may be listed in an almnac.