Interislander ferry the Kaitaki will be out of action for the rest of today because of problems with a backup generator.
As well as the cancellation of this morning's return sailing from Wellington to Picton, the night sailings have also been cancelled.
KiwiRail said a mechanical problem with the Kaitaki will be repaired in time for it to return to service at 8pm tomorrow.
Freight and passengers are being transferred to the Aratere where possible.
The Kaitaki has four power sources and runs on two at all times.
With one already out for maintenance, and problems with a second, the ferry does not have backup if another generator fails.