ancestors of Bernard McGrath

Searching for ancestors of Bernard McGrath born  1803 1875 married Silvermines 1851 Kilmore Country Tipperary Ireland.. Margaret Keogh. Two boys and a girl.from the marriage  somehow got from Ireland to Australia. For the life of me I cand find out from what port and how.  The girl married my grandfather Peter Bannah  giving her name as Delia Agnes McGrath, spinster from Newmarket Clare Ireland., The marriage was at  Maryborough Australia.23 December 1865.

 I would appreciate any ideas of how I could source new informaion

Thank you

Aubrey Bannah

email bk4ai@bigpond.com.