nearly all burial registers for IoM have been transcribed by IoM Fam History Soc - most of these have then been microfilmed by Mormons (Church LDS) and are available thru their film hire scheme. No unified database for burials exists however - however indices for 1851/61 etc census exist coutesy of the hard work of Brian Lawson
All are also in Manx Museum.
Civil records start 1877 onwards so unlikely to be caught by these
see http://www.ee.surrey.ac.uk/Contrib/manx/famhist/genealgy/index.htm