The MV Hebrides has badly damaged her starboard propeller shaft after chewing up heavy metal chains following a crash in Lochmaddy harbour.
Cal Mac said a "mechanical failure" caused the vessel to ground on the rocky bottom in the shallow inlet.
The ship's engines did not slow down despite the skipper activating the controls for reduced speed before the ferry approached the berth on Sunday, it is believed.
At least one engine appear to be stuck in the ahead speed and the ship continued forward, scraping along the rocky seabed.
The vessel appeared to have been steered to port. Where she ended up avoided a more serious collision and minimised damage.
She seemed to be expertly manouvered out of the tight predicament using a combination of her starboard thrusters and engine power.
Damage to her propeller shaft occurred after it became entangled with heavyweight anchor chains securing yacht pontoons.
Cal Mac said diving inspections also indicate that there has been some low-
However, her hull was not holed and vessel is watertight.
When the weather permits,
the Hebrides will begin the voyage to Greenock under her own power.
However, gale warnings are forecast for much of the week.
For safety considerations, the trip will be done in stages during lulls in the severe weather.
It is planned that she will enter dry dock on the Clyde at the end of the week.
Ferry collision caused heavy damage
27 September 2016
Photo: Ben Wear