CalMac said MV Loch Seaforth, the newest large ferry in its fleet, had developed problems with its engine control system with several sailings between Stornoway and Ullapool cancelled as a result.
In a fresh update posted, CalMac confirmed that the 7am and 2pm Stornoway to Ullapool sailings, and the 10.30am Ullapool to Stornoway departure were cancelled.
CalMac also said a review would be carried out at 2pm regarding the 5.30pm Ullapool departure.
The ferry operator also warned that there "limited capacity" was available on the alternative route via Uig-Tarbert.
Overnight freight services were also impacted with a number of CalMac ferries currently out of commission.
MV Caledonian Isles, MV Hebridean Isles and MV Clansman have not been in service since the summer timetable began on 1 April.
Robbie Drummond, the chief executive of the state-owned ferry operator, last month warned that the next two years will be "challenging" for island residents due to the age of the CalMac fleet with the a third of the fleet more than 30 years old, and almost half of its largest ships are beyond their expected service life.