The floating bridge will not return to action for several weeks, says the Isle of Wight Council.
The vessel, which provides a mobile link from Cowes to East Cowes, was expected to run imminently following scheduled maintenance.
Now, after more than three weeks out of service, another delay has been announced.
The Isle of Wight Council said: “A programme has been developed with our shipbuilders to carry out (the necessary) work.
“By the end of August we will know the cause, extent of the issue, date for completion of the works and return to service.
“The Isle of Wight Council apologises for any inconvenience caused by this ongoing disruption to the service.”
The launch service for foot passengers will continue to operate from 5am to 11pm Monday to Saturday and 630am to 11pm on Sundays.