David, You are very welcome.Have you tried Scotland's people?scotlandspeople.org
I just checked it to see and there are two Alexander Mowats married between 1842-1846 Aberdeenshire. Also 2 Mary Kilgours married between same years in Aberdeenshire. I don't know if they were married to each other without using credits. Also there is only one Mary Ann Mowat born for years between 1846-1848 Aberdeenshire. If you were to look at her birth record it will likely have her mother's maiden name. Scotland's people is done on a credit system. You purchase credits to use for your searching. I have used it many times and found many records of my Kilgour family. It is well worth using. It is important to try to narrow down the dates though so you don't have too many pages of names.