The ferry lost power with hundreds of passengers and cars aboard and began drifting July 29 on its way from Seattle to Bainbridge Island. It was eventually taken under tow and is still being assessed at a maintenance facility in Bainbridge Island's Eagle Harbor.
The interim director of Washington State Ferries told The Kitsap Sun the problem with the Tacoma is believed to be a switchboard that controls the ship's propulsion.
He says it could take a few more weeks before they get a repair plan from the manufacturer.
The ferry system has been shuffling vessels around Puget Sound and canceling or delaying runs since the Tacoma was taken out of commission.
The Tacoma broke down at the same time the 202-car Wenatchee was in a Canadian dry dock for repairs. The Wenatchee returned to service on Aug. 1.