The ferry brought in to replace the troubled Aratere will resume sailing this evening after breaking down in Wellington Harbour this morning.
Stena Alegra, standing in on a charter for the crippled Aratere, broke down in the middle of Wellington Harbour about 5am soon after it left on its routine early morning sailing for Picton.
Interislander general manager Thomas Davis said the ferry had been cleared to resume service with its scheduled passenger sailing from Wellington at 5pm today.
The source of a problem that caused two engines to shut down, affecting the control systems for one of the propellers, had been identified and repaired, he said.
"We apologise to our customers for the disruption this fault caused and thank them for their patience," Davis said.
The fault forced the early morning freight sailing from Wellington to Picton to be cancelled, as well as the return journey - a passenger sailing due to leave Picton at 9.05am carrying about 150 cars.
After the engine failure the ship was given a tug escort to an anchorage within the harbour where it remained until the Kaitaki ferry sailed out on its 9am sailing for Picton.
Stena Alegra then berthed under its own power at the InterIslander ferry terminal about 9.30am and some shipping containers and trucks were driven off the vessel.
Later in the morning Stena Alegra moved away from the ferry terminal berth to Aotea Quay, to a position where cruise ships normally berth.
Maritime New Zealand officials boarded the ferry to ensure it would be fully seaworthy before resuming service.
There was a light southerly wind in Wellington Harbour this morning and sea conditions were calm when the engine shutdown occurred.
The Stena Alegra made its first passenger crossing on Monday night, but has since been regularly holding up other sailings because of problems with its bow doors and stern ramp.
It sailed two hours late from Wellington on Wednesday morning, and more than half an hour late in the afternoon.
The Kaitaki was forced to stop in the middle of Wellington Harbour on both occasions on Wednesday while waiting to get into the shared ferry terminal berth.
Davis said the delays resulted from "teething problems with equipment, including issues with the raising and lowering of the ramp, some loading issues, and most recently an issue with the bow door.
"We can confirm that some improvements are being made to the bow door equipment by the ship's owner as a warranty issue."
Like Aratere, the 21,000 gross tonne Stena Alegra was built in Spain and has been chartered from its Swedish owners as a replacement for the Aratere.
Aratere lost its propeller on a sailing from Picton to Wellington on the night of November 5.
The Stena Alegra was previously operating on a route between Poland and Sweden, and ran aground during a severe storm in October last year.
NZ First leader Winston Peters said the Government should step in immediately and put a "qualified person in charge of the ferry service".
"The Government has been incompetent over this matter for years ... The present situation simply cannot be allowed to continue," Peters said.
KiwiRail had an uncanny knack of picking "lemons", Peters said.
"The Cook Strait ferry service is a farce. KiwiRail simply cannot get it right and it keeps making mistakes that are costing millions of dollars of taxpayers' money.
"The Aratere was a floating shambles and KiwiRail has simply replaced one mistake with another,"
- The Dominion Post