Bruce, apart from what Donna has written, more details are given from about 1849 onwards (depending on which parish), when places of residence, occupations, fathers' names and occupations, and (sometimes) ages are given, or at least whether "of age" (21).
I have photocopies and detailed transcripts only from Andreas, Braddan, and Maughold. I'll copy below some of the most detailed of typical entries from the period you gave. Most (about 60%-70%) of the entries have nothing other than the names of the people involved.
[Transcripts from Maughold register, with witnesses not usually transcribed.]
John Waterson / Cath Creech alias Taggart 28 Jul 1754
John of Kk Andrews.Cath aged 73 of Maughold.
Paul Gelling / Jane Gelling 27 May 1756
Mr Paul Gelling of Braddan and Mrs Jane Gelling
Patrick Kneal / Christian Stevenson 10 Jul 1756
Patrick from Jurby
Robert Stole / Jane Curlet 2 Feb 1765
Witnesses Robert Corteen farmer & John Christian Lague
John Corlet / Anne Cowle alias Corlett 17 Aug 1766
Mr John Corlet of Lezaire & Mrs Anne Cowle.
Anthony Priest / Jane Callister 24 Apr 1767
Anthony Priest Soldier .. of this parish.
John Frissel / Elizabeth Lewhellin 9 Jun 1768
Mr John Frissel & Mrs Elizabeth Lewhellin with father's consent.
James Hogg / Jane Davies 23 Jul 1774
With consent of parents.
Stephen McDaniel / Margaret Addison 2 Dec 1775
Widower & widow. Margaret from Bride.
Thomas Fargher / Margaret Cannell 23 Apr 1793
Margaret had guardians' consent.
William Killey / Mary Callow 2 Nov 1795
Mr William Killey from Liverpool. Miss Mary Callow.
William Kerruish / Catharine Kerruish 30 Mar 1799
William had guardians' consent & Cath had father's consent.
Anthony Huxtable / Ann Kermod 30 Apr 1803
Anthony late of North Britain but now of this parish.
Thomas Haines / Elizabeth Cullin 19 Aug 1805
Married in Elizabeth's house in Ramsey.
William Cooleish / Jane Quayle 12 Nov 1805
Signed as William Quillesh & Jane Quilleish.
John Douglas / Mary Scott 2 Jan 1808
Mary's signature looks more like Smith than Scott.
John Corlett / Hannah Summers 27 Apr 1813
John from Lezayre. Hannah with consent of guardians.
Edward Corkhill / Margaret Christian 7 Jun 1815
Mr Edward Corkhill widower & Miss Margaret Christian.
Thomas Fargher / Mary Summers 8 Aug 1815
With consent of parents & guardians.
Lunior ? Looney / Jane Kneale 2 Aug 1817
Jane had consent of parents. Could this be Simeon Looney?
[Comments from Tom Corteen, who transcribed from the original registers held at Maughold church.]
John Burgess / Elizabeth Bradford 2 Feb 1819
John an Ensign in 9th Sth Down Reg of Foot. Eliz from Ireland.
I hope these above examples are helpful, and give you a good idea of the kind of information which might be recorded at that time.
Sue