RootsChat.Com

I had a look at the Statistical Accounts of Kilchoman at https://stataccscot.edina.ac.uk/static/statacc/dist/parish/Argyle/Kilchoman

See screenshot, extracted from the New Statistical Account.
 
Also https://maps.nls.uk/geo/explore/#zoom=16.4&lat=55.74020&lon=-6.38733&layers=257&b=1&o=100 which shows that there was a Free Kirk in Port Charlotte. Why would the Morrisons traipse all the way to the Church of Scotland Parish Kirk at Kilchoman when there was an alternative on the doorstep? Unfortunately (as far as I can see) no registers kept by the Port Charlotte Free Kirk are in the care of the National Records of Scotland, and even if they ever existed they may not have survived.

Just doing a story of one Hunter family in Greenock, of whom a number emigrated to Australia.
I have access to Greenock Post Office directories but not 1841 census details to confirm occupations.

You have access to the transcriptions at https://www.freecen.org.uk/ but I personally prefer to use the original site at https://freecen1.freecen.org.uk/cgi/search.pl - I think it's much easier to use and the results are better formatted.

Coverage of Renfrewshire is complete for 1841 to 1871.

I note with interest that a search for surname Hunter in Renfrewshire in 1861 produces 742 results on the original FreeCEN site, but if you run the identical search on the new FreeCEN site it asks you to refine the search to produce a maximum of 500 results.

Just out of curiosity, I searched for surname Smith in Renfrewshire in 1861, and the original FreeCEN site asked me to refine the search to find a maximum of 1500 entries.

Interesting, thank you Forfarian.
and that answers why I started to wonder . .
as despite it being 'compulsory' if e.g. a couple, newly arrived from Ireland nipped along to the local Parish Priest, had banns read, got wed and given a schedule (which they likely couldn't read) -  and then promptly moved onward south of the border (or further) then the marriage may well not be recorded in the Statutory Registers.
and the chances of finding them to issue a fine of up to ten pounds are pretty remote - even if they stayed in Scotland.

Indeed.

James - Head - Mar - 49 - Labourer - Kilmichell Glassery
Mary - Wife - Mar - 35 - No trade - Port Charlotte, Kil .... (Cannot make it out)
John - Son - Unm - 15 - Labourer - Port Charlotte, Kil .... (Cannot make it out)

Port Charlotte is in the parish of Kilchoman. See https://stataccscot.edina.ac.uk/static/statacc/dist/parish/Argyle/Kilchoman

The parish of Kilmichael Glassary is on the mainland of Argyll. See https://stataccscot.edina.ac.uk/static/statacc/dist/parish/Argyle/Glassary

"Upon production of a certificate of proclamation of banns or or publication of notice .... the contracting parties are entitled to be furnished with a Marriage Schedule by the Registrar of the district wherein the marriage is solemnised .... The Marriage Schedule is a legal document of the greatest importance, and should be completed with the utmost care and accuracy .... the Schedule shall be given to the married parties, who, within three days thereafter, shall either deliver it or send it by post to the Registrar .... and in case of failure to do so, the husband, and failing the husband the wife, shall be liable to a penalty not exceeding ten pounds. On being received by the Registrar, the contents of the Schedule shall forthwith be entered by him in the Registers ...." [G T Bisset-Smith, Vital Registration, Edinburgh 1902 - this is a 'Manual of the Law and Practice concerning the Registration of Births, Deaths and Marriages']

So the law places the responsibility squarely on the couple themselves to ensure that the Schedule reaches the Registrar.