Thanks to you all for all this information.
The Thomas Crebbin I'm looking for is married to Catherine Moore, born in 1832 I believe. If I've gone back correctly he's the father of John Crebbin (1867), father of William Edward Crebbin (1908). The seemingly lack of imagination in names at this time causing me a few problems. From the Rushen gravestones I have Isabelle and Elizabeth as their other children, but they died in 1877. William is another brother to John from the IGI, born 1878, so this seems to be the same family mentioned by Bruce.
I have Thomas as the son of John C & Jane Karrran as well- its reassuring to hear someone else with the same info! From the possibles here it looks like he was on the "Nellie".
If anyone else has information on this part of the Crebbin tree I'd like to share info.