Hi
I'm not sure that the man in America is the same as served on HMS James Watt. I say this because the Crimean War only started in 1854, and there is a navy service record for a David Owen, born Glasgow, 6 July 1826, who signed up for continuous service in March 1854. If you have not already done so, it might be worth purchasing this record to confirm (a) if this man served on HMS James Watt and (b) if he had prior navy service, and what the dates of this service might be. What is interesting is that the Baltic Medal roll suggests that the man on James Watt may have 'Run' - deserted.
http://discovery.nationalarchives.gov.uk/SearchUI/Details?uri=D7539563Find my Past, in their Merchant Seamans records have the Ticket for a David Owen with the same date of birth as the man on the above naval record, which shows that prior to 1849 he had served 9 months with the Peruvian Navy.
HMS James Watt was not chartered to the British Navy, but originally ordered as HMS Audacious a 91 gun battleship, but was re-ordered as a screw battleship in 1847, and launched in 1853.
Martin