Hi Richard, I have a Wendron Marriage Register 1754-1812, pg. 269, entry no. 1863, for an Elizabeth Tyack of this Parish who married William Morcom of the Parish of Gunwallow, By Banns, on the 26 December 1809, by Thos. Trevellian, Curate. In the Presence of James Tyack and James Oliver.
William Morcom/b's father also a William of St. Mawgan & St. Martin in Meneage, sp. of Phillipa nee Williams, was deceased July 1802. William Morcom/b and Elizabeth nee Tyack, went to live in St. Mawgan in Meneage where he was blacksmith 1787-c1814. This family moved then to Gweek in the Parish of Constantine where they stayed until immigrating emb. October 1851 to South Australia per barque "Charlotte Jane" Elizabeth Morcomb (nee Tyack) contracted dysentry aboard the "Charlotte Jane" and died 22 November 1851 and was interred at sea.
I know little else of this Tyack family and suppose Elizabeth was the dau. of a James & Arminel Tyack, bn/bapt. 6th April 1788 Helston, resident of Wendron. Ref. OPC Births - Helston
No Gunwalloe BDM entries for Morcom/b Morcom/b relatives also were blacksmiths at St. Martin's (Green) How William Morcom came to be at Gunwalloe is only speculative - possibly grandmother's Duncalf relations?- bonded apprenticeship(blacksmith)? or military service(Miner's Militia)?
Does this Elizabeth Tyack fit into what you know of James Tyack and Ann Treloar?A sister maybe? Regards, Paul. A. Morcom Geraldton. Western Australia.