KiwiRail has revealed a leak in the Interislander Kaitaki ferry’s engine cooling system is what caused the ship to lose all power.
A mayday was declared just after 5pm on Saturday with 864 people on board after all four engines shut down.
The ship was eventually able to regain some power and made it back to shore, accompanied by several other vessels, including two tug boats.
No one was injured.
Interislander executive general manager Walter Rushbrook said the root cause was a fault in the ship’s engine cooling system.
“A leak occurred in a connection that is part of the cooling system, which resulted in a loss of pressure,” Rushbrook said.
”Sensors in each of the engines detected the reduction in pressure and the engines automatically shut down to protect them from overheating.”
Rushbrook said the crew quickly isolated the fault and were able to restore power to the ship.
”The crew rapidly isolated the fault and were able to restore power to the ship.
The connection has been repaired and all other parts of the cooling system have been checked and tested, Rushbrook said.
“Safety is our number one priority and we will not resume sailing until we are certain it is safe to do so.”
Rushbrook said the ship will not return to service until Lloyds Register Class Society, an independent third party, has inspected the ship and issued an assurance report to Interislander and Maritime New Zealand.
He said KiwiRail appreciated the situation was hugely disruptive for people trying to travel at one of the busiest times of the year.
The disruption has caused a backlog of passengers and freight.
Some sailings have been rescheduled and the Interislander’s other ferries have been doing extra trips to try to get as many people across the Cook Strait as possible.
Interislander’s contact centre has been experiencing high call volumes and long wait times so people have been asked to make bookings and cancellations online where possible.
”All those affected have been notified individually. We apologise again for the impact this disruption has had on people’s plans and we are exploring every option to relieve the situation,” Rushbrook said.
It’s hoped the Kaitaki will be sailing again as soon as possible later this week.
”We will be undertaking sea trials and initially it will carry only freight before returning to normal service. We will confirm the timeframes for this as soon as we are able,” Rushbrook said.
The Transport Accident Investigation Commission has opened an inquiry into the incident.
The chief investigator of accidents, Naveen Kozhuppakalam, is appealing for ferry passengers and residents of Wellington’s South Coast who have videos or photographs of the events to contact TAIC at info@taic.org.nz.
A team of investigators with expertise in marine operations, engineering and maintenance will now look into what caused the incident.
Their initial investigation work will be to interview the ship’s crew, incident responders, Wellington harbour authorities, and other witnesses.
Aircraft ordered and due to arrive and begin operating in September 2026.