I did search there and on other websites. I found the chap born in Nova Scotia but he didn't fit the bill. I didn't see one born in Armagh so I will take another look. I was told by my Grandmother that he was the captain of a ship travelling between Liverpool and New York. Some of his children were born in New York but are registered in Liverpool. His wife was in Liverpool and still married in the 1861 census, the children were still with her. Again in 1871 she is in Liverpool but an Annuitant so she must have been receiving a pension following his death. In 1881 she has remarried and Austin's children are with her and her new husband.
It's all very curious but I will try the Merchant Navy records again.