I think we can discount 'Captain Glen'. The earliest reference I have is for c1770 and none of the broadside versions I have actually have that as the first line. It's the second line that is like the above song. First line of the 'Captain Glen' versions usually runs 'There was a ship and a ship of fame', and its 'New York Trader' spin-off starts with 'To a New York trader I did belong'.

Unless we come up with yet another ballad with that first line then I'm happy with the 1748 date.