Rob, the Maughold parish register has a marriage between John Cannell & Margaret Cannan on 20 Oct 1711, but there is no indication of his age or where he was from.

That b.1681 looks like someone's invention, and you need a source for it to have any validity. There was no bapt in Maughold for John Cannell at or near that date. Early Maughold Cannell wills could help identify this couple.

Please see my response to Tim, below.

Sue