Hi Lisa,
I too, am of McNab(b) descendancy, but don't have any info which may be relevant to your Captain John McNab. My "McNabs" were from Glasgow as from about 1860's, (having come across from Ireland, possibly Co. Tyrone). We used to think that our McNabs were of the "Killin McNabs" - the original clan being from a lovely little town in Central Scotland called Killin, - but it turns out we are more Irish than Scottish. I presume you will have some knowledge of the original McNab history? And of the "McNabs" who a strong presence in your native Canada?
(by the way, we sort of believe that the McNabb with double B was more of an Irish version of the name, but many changed it to McNab after moving over to Scotland - often after the Irish Famine in mid 19th century)..??
Anyway - sorry, I can't offer much help - but wish you all the best in your research.
Maggs
If your still searching and have any more information since this was written i would be so appreciative,,,,,,i am loosing my hair trying to figure out how to find my ggg grandfather now Adam Mcnab.......He just seems to drop off after his two boys were very little, and then i get nothing.....no matter what i have read. I think my search may have come to a complete stop, as i have read that many seafarer families didnt have registrations, or even wrote down births/marriages or deaths....uggg.....i cant even get my own father to send me a thought..oh dear!