That pic of Caledonian MacBrayne's MV Isle of Lewis which runs between Ullapool and Stornoway (2h 45m) was taken by Chris Murray who used to work on the Stornoway Coastguard Helicopter. He used to take his camera to work and has some stunning photographs which you can see here.
Anyway, ask anyone nowadays what they understand by "a steamer" and they'll probably think of Scotland's "Waverley" or something on the Swiss lakes - something that only comes out in summer to take people on jollies and spends the rest of the year under tarpaulins with volunteers and lottery funding applications. This is a steamer:-
But the present day connotations of "ferry" and "steamer" only date back to the 1960s and the development on a meaningful scale of car ferries - i.e. ships designed to allow their passengers' cars to be driven on board. Before then, a "steamer" was the sort of vessel we would now call a "ferry" (a ship for the purposes of getting from A to B) and "ferry" meant something altogether different.
Until the 1960s "ferry" meant either the crossing of a narrow estuary or loch (such as the Corran Ferry across Loch Linnhe) as it still does today or another meaning which is now entirely forgotten - a launch which went out to meet a steamer at a port of call where there was no pier the steamer could get alongside. These were called "ferry calls" and used to be very common in Scotland. The following picture (courtesy of Rob Beale) demonstrates the old terminology well:-
The caption is "The Ferry, Craignure (M.S. "Lochinvar" Making A Call)" but the ferry referred to is not the ship pictured, the M.S. Lochinvar - she is the steamer. Rather, the ferry is the rowing boat to the right which has gone out from the old stone pier at Craignure on Mull to meet the steamer which has stopped en route from Tobermory to Oban.
What's interesting is that the "steamer" pictured in Rob's postcard is not a steamship at all - the Lochinvar was a motor vessel. MacBrayne's were quite forward thinking in terms of ordering motor vessels as opposed to steamers, the Lochinvar dating back to 1908 being their third. Other companies - such as British Rail - were still ordering steam powered ships in the 1960s. But the old terminology stuck even amongst MacBrayne's fleet with diesel powered motor vessels continuing to be referred to as steamers.
It all comes out very clearly in MacBrayne's 1955 summer timetable.
It contains a list of the "Steamer Fleet" but, of the 21 vessels named, only four are actually steam powered. It also contains a list of "Steamer Fares" but is careful to indicate that these don't include the ferry fares where in operation. There were nine ferry calls in the MacBrayne network in 1955: Colonsay, Craignure, Drimnin, Coll, Eigg, Rum, Glenelg, Applecross and Rodel.
Car ferries were introduced on some of MacBrayne's services in 1964 and timetables in the late 60s distinguished between "Car Ferry Services" and "Steamer Services", although by then only one of the latter was operated by an actual steamship and that was a summer only cruise (The SS King George V from Oban to Staffa and Iona.)
The building of piers at Colonsay, Craignure and Coll in the mid-60s combined with the cessation of calls at Drimnin, Glenelg, Applecross and Rodel meant the only remaining ferry calls in the late 60s were at Rum, Eigg and Muck (the latter island having been added to the network in the interim). From now on, timetables referred to the vessels taking you ashore at these islands as "ferryboats" to distinguish them from the ferries - i.e. car ferries - which were increasingly dominating MacBrayne's fleet. Ferryboats were sometimes also referred to as "flitboats".
Ferries - in the original sense of a launch which came out to meet a ship at a place where there was no pier it could get alongside - disappeared from the West Highland scene in 2001 with the opening of piers at Rum, Eigg and Muck. I leave you with a picture of the Eigg ferry (or ferryboat or flit boat if you prefer) coming alongside Calmac's MV Lochmor in the late 80s - arguably the last "steamer" in the fleet in the sense of a ship not designed for cars to be driven on to.