MV Loch Seaforth, which sails between Ullapool and Stornoway, is out of action following a problem with a ramp.
Scotland's political leaders turn their attention to the problems facing ferry services as campaigning continued for Holyrood.
The vessel, which sails on the busy Troon to Arran crossing, only returned to service last week following previous repairs.
Procurement for another new CalMac ferry begins but the GMB union says UK-based shipbuilders will struggle to compete with firms in "low-wage economies".
MV Lord of the Isles, which was covering the Oban to Mull route, will be ready to deploy again "early next week" after problems with its main engine.
The west coast ferry operator says forecast gusts of up to 90mph could further disrupt services already stretched due to a shortage of vessels.
MV Isle of Islay is the first of four large new ferries ordered from a shipyard in Turkey.
John Swinney has expressed his regret as CalMac confirmed eight vessels were out of action.
MV Lord of the Isles, which has been sailing the Oban to Mull route, suspended all sailings on Saturday.
