In a previous post (John Mason - where did he come from?) I explained my reasons for thinking that the John Mason who married Catherine Murphy in Sydney in 1841 was probably the convict named John Mason who was tried and sentenced to transportation for stealing cotton in Limerick, Ireland, in 1833. He arrived in Sydney on the Parmelia in 1834.
However, there were still several other convicts who could potentially have fitted the bill. The next most likely after 'John from Limerick' was a John Mason, born in 1813, who was tried in York in 1835 and transported on the Royal Sovereign. I've now discovered from the New South Wales Convict Indents 1788-1842 (on Ancestry.com.au) that this John Mason was Protestant, and could read and write. Which means that he is very unlikely to have been the John Mason who married Catherine in a Catholic church, and who signed his name with an X.
Another small piece of information I gleaned from the New South Wales Settler and Convicts list, 1787-1834, was that the John Mason who arrived on the Parmelia was assigned to an Alexander Fotheringham in Sydney. As yet I haven't been able to find out much about Alexander Fotheringham except that he seems to have been a shipwright who owned several properties around Sydney.
If you would like a copy of a spreadsheet listing all the details I could find about 19 of the convicts named John Mason who arrived in NSW before 1841, please contact me and I'll email it to you.