Greg, having looked at various trees on Ancestry, I can’t see any reference to a date when Thomas Taggart sailed to Australia. I’ve now found one possibility (June to September 1854 --- details and link below). The 32 year old has a blank in the “occupation” column, but the previous passenger on the list (with a wife and family) was listed as a joiner. Perhaps Thomas Taggart should have had ditto marks for occupation ?

If that hunch is correct, then the 1841 and 1851 census entries below might be your Thomas Taggart. He could have sailed off in 1854 and had plenty of time to meet his future wife and marry in 1856.

I wouldn’t worry about the discrepancy in ages given by Thomas. It was common to knock a few years off your age. Thomas was actually baptised in 1817.

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1841
Cheshire

Name: Thomas Taggart
Age: 20
Estimated Birth Year: abt 1821
Gender: Male
Where born: Foreign Parts
Civil parish: Bidstone
Hundred: Wirrall (Lower Division)
County/Island: Cheshire
Country: England
Registration district: Wirral
Sub-registration district: Woodchurch
Neighbors: View others on page
Piece: 126
Book: 3
Folio: 4
Page number: 3

Note: image shows Thos Taggart, journeyman, lodging with Joseph Bagley, carpenter and his family.
Born in “Foreign Parts” means “not England, Scotland or Ireland” and was often used for people living in England who were born in the IOM.

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1851
Clarence Street, Liverpool

Thomas Taggart 31 unmarried joiner and builder b IOM

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Victoria, Australia, Assisted and Unassisted Passenger Lists, 1839-1923 --- Ancestry’s transcription:

Name: Thos Taggart
Nationality: English
Arrival Age: 32
Birth Date: abt 1822
Departure Place: Liverpool
Arrival Date: 25 Sep 1854
Arrival Place: Melbourne, Australia
Ship: John and Lucy

Note:
The actual images are sequenced so that I’d put a question mark over whether the ship name is more likely to be the “Oliver Lang” (judging by the running totals of passenger numbers etc)

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Jean C