I show the marriage date for William & Margaret Drummond to be 1 Jan 1784 in Shapinsay, Orkney.

Possible marriages based on age taking place on Shapinsay
John Bews 2 Apr 1805 to Margaret Hutcheson
Margaret Bews 24 Dec 1805 James Nicolson
Christian Bews nothing found in Shapinsay
James Bews nothing found in Shapinsay
Peter Bews 27 Oct 1825 Mary Laisk(Leask?)

I have a small database of birth and marriage records indexes from the Orkneys on my website which is where I got the above.

If interested check out
http://tilley.dynodns.net:8000/modules.php?name=OPR