Hi Veryan,
Thanks for the thoughts. I must admit that many of them had crossed my mind too!

I have tried Lloyd's Register of Captains, where I have found my Doughty's before, but if I'm not mistaken the letter "S" was not transcribed. I will look again.
I did a quick search now which brought up a John Stirling born 1808 / 1818 Forfarshire, listed in the Merchant Navy Seamen Records, with service between the dates 1845-1854

The only mention I can find of a likely Stirling in Queenstown, is in the Cork Examiner 22 October 1863-
"A FIRE which might have borne very fatal consequences, but which was fortunately discovered in time to prevent serious injury, occurred on Wednesday evening in the house of
Captain Stirling at Queenstown. A servant had carelessly left a night light burning on a wooden mantel-piece in a bed room where some children were asleep. The light having burned down set fire to the timber which blazed up. A chimney glass which stood above it was next caught by the flame, and it cracked and broke and fell with a loud crash. It was this noise which providentially attracted the attention of the servants who were below stairs, in time to rescue the sleeping children, and to have measures taken for the suppression of the fire."