You can certainly search on the IGI - there are batches covering the Isle of Man. If you follow this link and then follow the instructions you may find some of your ancestors:
http://freepages.genealogy.rootsweb.ance…
The various UK census (1841 - 1911) also cover the Isle of Man. You can search the 1881 census for free but all of the others you need to have a subscription to one of the genealogy sites ie Ancestry or Find My Past. There is also Freecen but I don't know if they cover the Isle of Man.
A good resource is Rootschat which has a board dedicated to the IOM - lots of very helpful people who will be very knowledgeable to researching ancestry on the IOM: www.rootschat.com
I've had a look at www.freebmd.org.uk but can't see that it covers the IOM but maybe someone else on here can tell you if it does.
Good luck

