Bill, I think i remember as a boy there was one other the King George V which came into Campbeltown.
You'd need to be quite long in the tooth to remember the KGV on the Campbeltown route (of course, maybe you are!). She was built in 1926 to run from Greenock (Princes Pier) to Campbeltown or Inveraray but was transferred to David MacBrayne's fleet prior to the Second World War. They moved her to Oban and put her on to summer season excursions to Iona and Staffa, which she resumed after the war until 1974, when she was withdrawn. In winter she returned to the Clyde and was from time to time seen on the Ardrishaig route (Greenock-Gourock-Dunoon-Innellan-Rothesay-Tighnabruaich-Tarbert-Ardrishaig and return).
Campbeltown folk are more likely to remember the St Columba on this route. She was originally the Queen Alexandra of 1912 and ran to Campbeltown from Fairlie in her early years until, like the KGV, taken over by MacBrayne's in 1935. They re-modelled her adding (among other improvements) a third funnel. She was bigger than the Hamilton or the Montrose and very well appointed. After the St Columba was withdrawn in 1959 the vessel most likely to be found on the Ardrishaig route was the Lochfyne. She was powered by diesel electric engines and what I remember most about her was that these gave her quite a bit of noise and vibration, unlike the turbines, which were virtually silent and absolutely vibration-free. Her winter season replacement was usually the Lochnevis.
The Gourock-Campbeltown route was indeed summer only (May to September), leaving Gourock at 9.25 and arriving in Campbeltown at 1.40, leaving again at 3.15 and getting back to Gourock at about 9 in the evening. The route was Gourock-Dunoon-Rothesay-Largs-Fairlie-Lochranza-Campbeltown and the reverse (obviously) for the return journey. Folk going to Glasgow or beyond usually got off at Fairlie, where they could get a limited-stop train to Glasgow getting in about half past six. The steamers on this route were the Duchess of Hamilton and occasionally the Duchess of Montrose. They were virtually identical, except that the Hamilton had a cross-spar on the mainmast. My Aunt Jean's father was Chief Engineer on the Montrose, but despite that the Hamilton was always my favourite. To my knowledge the Waverley never ran on scheduled services to Campbeltown, though she did make occasional appearances on excursions. After the demise of the Montrose (1965) and Hamilton (1972) the Queen Mary II (the numeral is important) ran to Campbeltown for a couple of seasons before she too bit the dust. The last vessel to appear on the route was the car ferry Glen Sannox, a complete disaster (despite the tables and parasols (!) they put on the open car deck) compared to the glory years of the turbines.
Sorry to put up such a long post, but I'm a bit of an anorak when it comes to the old Clyde steamers.