Yes, IOM wills are often a terrific source of information, being far more detailed than English ones I have seen, and involving far more "ordinary" people.
See: www.iomfhs.im/lawsons/wills/mo-will.html where you will find some transcripts attached to the index entries. Brian Lawson, who compiled that database, transcribed two William Moore wills which are a good example of the amount of information that might be given. (One from Lezayre, and one Maughold.)

This looks like a very good possibility to be your James:
MOORE, James 1867 Lez E[pis] will no.8, on LDS film no. 0106471

You can order and view LDS films for a small fee through their Family History Centres worldwide (in phone book under Church of Jesus Christ of Latter Day Saints), or in the Manx Museum Library.

Sue