Alex, there are many early indexes and some records online for the IOM.

See FamilySearch.com for the IGI (index to bapts and marriages), and for full transcripts of the 1881 census.

For burials see: www.iomfhs.im/lawsons/burials/_bur_index.html

For mainly later births (civil regt) see: www.iomfhs.im/lawsons/births/_bir_index.html

For registered marriages see: www.iomfhs.im/lawsons/marriages/p_mar.html

For census indexes see: www.iomfhs.im/lawsons/census/census_index.html

See also other databases under "Research" at www.iomfhs.im

When you have worked out names and dates see: www.isle-of-man.com/manxnotebook/ Use the "Search page" facility.

The 1861 census of Onchan has:
James Pearce Head, 47, Fisherman? (Dreadful writing), can't read where born. Ancestry.com says Douglas, but that looks wrong - perhaps someone who has the CD or fiche can help you?
He is with wife Mary A Pearce 40, and children b.IOM: Esther Pearce 15, James Pearce 16, Joseph Pearce 14, Wm Pearce 11.

James Henry Pearce bapt 15 NOV 1844 Saint Barnabas, Douglas, son of James Pearce & Ellen. Also:
Joseph bapt 23 APR 1846 Saint Barnabas, Douglas; Ellen 11 MAY 1852 Saint George, Douglas [IGI]
The IGI has a marriage of James Pearce to Ann Cannell 23 APR 1853 Braddan (could be Mary Ann).

The burials (website above - please read the explanations there) have:
PEARCE, Ellen [ aged] 33 Bra 10 May 1852
PEARCE, Ellen 10 wks Bra 16 Jul 1852
PEARCE, James 58 Bra 22 Oct 1878
PEARCE, Mary Ann 65 Bra 19 Feb 1878

Sue