A creel was being blamed for the damage to the MV Isle of Lewis, causing the vessel to be withdrawn and taken to a dry dock in Greenock.
CalMac had to juggle the network to replace the ferry, which carries up to 123 cars on the Ullapool to Stornoway route. The ferry Hebrides, which can take 90 cars, had to leave its Skye/North Uist/ Harris service. She in turn was replaced by the Islay ferry Finlaggan.
A CalMac spokesman said: "When in dry dock it became evident some minor repairs to the hull steelwork were needed. We are hopeful she will be ready to return to Stornoway in a few days' time, probably on Thursday.
"We are confident there are no capacity issues as a result of the MV Isle of Lewis being taken out of service for this essential work."