Have you used the IGI.
If not go to www.familysearch.com
Type in: James Gelling
On the right select: IGI/British Isles
Click: refine search
In the year range enter: 5
In the year enter: 1818 (he was 43 in 1861)
In Ccountry select: Isle of Man
You will get the James Gellings born between 1813 and 1823

Note that in the 1841 census, there are two potential James in Douglas age given is 20 (meaning agred 20 - 24 at the date of the census).
One is in Douglas District 5 on page 4 entry 19 living with a 13 year-old Richard Gelling.
Using the IGI, you should be able to find out which Richard and James had the same parents.
The second is also in Douglas District 5 on page 20 entry 87. He was living withCatherine Gelling 14 and Elizabeth 55.
Neither of these two James appears in the 1851 IOM census. So it looks as though they had both left the island.