Hi Barry

You never mentioned your relationship to Robert Clucas , I did some more research and found that he and wife Catherine O'Brien were married in St Mary's Cathedral in Sydney , so he must have changed his religion.
The ship he arrived on "Adam Lodge" had Gilchrist & Alexander as it's agents , and they were the same agents that looked after the "Gazelle" that he went down on.
On the "Adam Lodge" ships documents , Robert could not read or write.
On board were 215 Irish , 27 English and 9 Manx. Other Manx were
Couples James & Esther Commash , James & Ann Cormode , single males , John Christian , William Crane & Robert Gill , and one single female Jane Moore.
Robert & Catherine O'Brien appear to have had one child Margaret Ann Lucas , born 1844 , who marries Thomas McGuigan , in Paddington , Sydney in 1869 and dies 1900 , Margaret and Thomas have some children maybe up to about 8 , but it is confusing , could be two couples having children.
Did you find the article on the sinking of the Gazelle with the crew named ? I could email it to you if you like.
My concern is that the other Robert Clucas who died in Sydney in 1859 is shown in an article as a "Masrer Mariner" , ie Captain , could you have the wrong Robert Clucas ?
Cheers
David