Re: James McSherry abt 1824 - 1880 mariner of Toronto, Ontario.
William Perkins Bull, a Peel County Historian, made a reference in his notes on early settlers in Peel County back in the 1930's, that Peter McSherry of Toronto Township was related to the McSherry's that worked the lake boats.
I have not been able to make a definitive connection yet.
I don't know the basis of Perkins Bull's claim.
Peter McSherry 1775-1838 was one of my Great-great-great grandfathers.
In the records of St Michael's in Toronto I came across the baptismal record for Patrick McSherry, son of James. The parents were listed as James McSherry of Armagh, Ireland and Margaret Herbert of Tipperary, Ireland. 16 April 1858, Page 5 Book 1
I don't doubt that James may have been from Co.Down.
I did a GedCom on this family listing what I could find on James and Margaret's descendants which I will send to you.