Lonan is a difficult parish, lots of missing entries, and minimal information in the period you're looking at. I researched the Scarffe's a number of years ago because I have Scarffe in my ancestry. I think Thomas Scarff was bapt 24 Oct 1762 s/o Philip Scarff & Ann Callister. He married Eleanor Kewley 16 Jun 1787 Lonan, 8 children 1788-1804.
Potential parents for Eleanor Kewley are Patrick Kewley and Margaret Watterson, md 9 May 1752 Lonan. Baptism for this Eleanor is 11 Mar 1764. Thos & Eleanor's eldest daughter was named Margaret, which is a good sign, though no Patrick amongst 4 boys. It doesn't feel right to me, though. Eleanor made it to the 1851 census at 6 Water Lane, Douglas, "Mother Widow" age 90 with son William and his family. She is 93 when buried in Lonan "from Douglas" 2 Apr 1853. If those ages are right (and we know they can get exaggerated when that old), she ought to have been born about 1760 or 1761. Unable to find her in 1841.