the Whitehaven censuses provided the following estimated YOB's for James Callow
1841 YOB circa 1786 but rounded down
1851 YOB circa 1787
1861 YOB circa 1785 (in the Oreston Workhouse)
died 1868 at the Preston Workhouse YOB circa 1785
If you make a search of christenings on the IGI between 1780-1790 there are no James Callows chr. in 1785 in the IOM

There are two James Callows one chr. 1787 Maughold and one chr. 1788 Ramsey that can be discarded.

James Callow chr. 1787 Maughold was buried 1871 Maughold. Was part of the Callow the Dhullan family (source Constance Radcliffe chart of this family.)

James Callow chr. 1788 Ramsey was buried 1852 Maughold (source Joyce Oat's PAF and burial register)

That leaves:
1) James Callow chr. 1788 Lonan parents the eldest son of Patrick Callow (my 3rd great grandfather) All I know about this James Callow is that he left the Island and I have no further record of him.
2) James chr. 1787 Lonan father William Callow is a strong possibility but the gap of 8 years between his birth and the youngest child of William Callow and Margaret Kelly (married 1771 Lonan) is puzzling. William Callow left no will but is mentioned in his mother's will of 1799. He died in 1800.

Patrick Callow and the above mentioned William Callow were brothers and part of the Croit Roie Callow Family of Lonan who can be traced back a number of generations.