I could not find the family on the 1841 census either UK or IOM, so you are assuming he may have returned to the IOM.
He is a bit interesting as I cannot find his birth. There is no birth of a James Crebbin to William from 1828 to 1843.There is no doubt that this James shows his birth as Douglas on his MC and census , his DOB is 1833 in 1871 and 1836 in 1881.
On the IGI there is a user sponsored entry showing his MC to Jane Cowley , but gives his ch 21/12/1837 Douglas to Thomas and Margaret. The original MC is absolutely William , but James is shown as Illiterate but not Jane , and she would surely know her husband's father's name.
William Crebbin is not shown as deceased, so maybe the family came back to the IOM.
I found two James Crellins born Marown 1839 and Patrick 1830 with father's William.
So this James is a chance. Will keep looking