Rough seas are forecast over the weekend while authorities work on an operation to tow the beleaguered MV Shiling cargo ship to Wellington harbour.

The vessel lost power 22 nautical miles from Farewell Spit and issued a mayday call on Friday. An ocean-going tug from Port Taranaki, Skandi Emerald, was dispatched and safely secured the troubled vessel which has been anchored at Tasman Bay since Saturday.

It’s still unclear exactly when the Shiling will be able to be towed to Wellington. A passage and towing plan needs to be confirmed and the operation will be weather dependent.

MetService meteorologist Thapi Makgabutlane said winds are expected to pick up between the north and south islands from Friday evening.

They will remain strong for most of the weekend, she said.

“Very rough seas are expected through to the end of Sunday, as well as moderate swells.”

Multiple helicopters and a Defence Force Hercules were sent to Shiling’s mayday call where the 294m vessel was drifting in rolling seas.

The 24 crew members had been preparing to abandon ship but ended up staying on board.

Incident Controller David Billington said Maritime New Zealand’s priority was to undertake the move from Tasman Bay to Wellington as safely as possible.

Yesterday those on board the Skandi Emerald were swapped out for a fresh crew, he said.

Supplies have also been delivered on board Shilling and a towing expert has boarded.

The expert will support the connection between the two vessels, the tow plan, and the voyage to Wellington, Billington said.

It’s the fourth incident involving the ship that New Zealand authorities have dealt with in the past year.

Shiling lost power in April when it was leaving Wellington Harbour.

Repairs were required to the ship’s generators and main engine; however, permanent repairs could not be done in New Zealand.

Temporary repairs were completed to a standard thought to give Shiling sufficient engine power to sail to Singapore for a permanent solution.

Instead Shiling again lost power, this time in open water.

Maritime New Zealand said it only released Shiling from detention after the vessel’s classification society, Lloyd’s Register, confirmed it was satisfied with repairs to the ship’s generators and main engine.