Repairing Interislander could take months - KiwiRail

The Interislander ferry Aratere sailing across Wellington Harbour. Photo / Mark Mitchell

Replacing a propeller which fell off an Interislander ferry during a Cook Strait crossing could take up to nine months, KiwiRail says.

Passengers on Tuesday's 6.30pm sailing on the trouble-plagued Aratere were told by crew that a shaft had snapped and a propeller had been lost near the entrance to Tory Channel.

Interislander general manager Thomas Davis said they were trying to identify the location of the propeller in a bid to recover it.

"Furthermore, it would be very helpful in understanding the nature of the failure," he said.

The propeller was worth around $200,000.

KiwiRail wouldn't have any confirmation on costs of recovery until the propeller's location was identified, he said.

The recovery cost would then be weighed against the cost of a new one.

Producing and delivering a new propeller would take around nine months, Mr Davis said.

It was unknown how long Aratere would be out of service, and a temporary replacement ship was being considered.

More than 500 passengers due to sail on the Aratere had their bookings shifted and hundreds more were believed to have cancelled theirs.

KiwiRail had stopped taking any bookings until further notice, a KiwiRail spokeswoman said.

The Transport Accident Investigation Commission is investigating the incident.

Greg Miller, director of freight company Toll New Zealand, declined to comment on the amount of freight the company had sitting on the wharf in Wellington as a result of Aratere's breakdown.

"There's an element of frustration given the time of the year and the fact that Christmas volumes are building," he said.

Toll NZ shipments had been delayed by 24-48 hours by Aratere's breakdown and contingency measures were in place to move freight, he said.

"Obviously we're working with the Interislander on a solution, given the volume that we move on the ferries."

The Aratere recently underwent a $54 million revamp, but had been plagued with problems in recent years.

In January, a computer issue affecting the propulsion took it out of action, and engine problems put a stop to passenger sailings for more than a week in 2011.