The beleaguered Aratere interisland ferry is slowly returning to Wellington after being worked on in Singapore.
InterIslander general manager Thomas Davis said KiwiRail expected the ship to arrive in the first few days of July and the company was now planning for her re-start on the Cook Strait run.
He acknowledged the vessel's return was later than anticipated.
"Given the seriousness of last November's shaft failure, we have adopted a very vigorous approach of reviewing all systems on the ferry, both in terms of repairs and the maintenance programme that was carried out.
"We are taking the approach that the Aratere will only return to service once we are confident that all tests have been passed to the satisfaction of KiwiRail and regulatory authorities," he said.
Passenger services would not be affected as it was the low season and all bookings could be fully accommodated on the Kaitaki and Arahura, Mr Davis said.
Problems have continued to dog the ferry however, with one engine out of action due to mechanical issues.
The engine had not "blown up", rather it was the sort of fault that occurred from time to time in any vessel, Mr Davis said.
Once back in New Zealand and before she could resume service, a range of tests must be undertaken and re-equipping carried out.
This was expected to take about a week to complete, he said.
Maritime New Zealand would undertake an audit before re-issuing the ship with a Safety Management Certificate.
The Aratere has been in dry dock in Singapore following a propeller shaft failure in November.
Apart from the repair work needed as a result of that event, the vessel has also undergone her full two-year maintenance programme while she was laid up, Mr Davis said.
The work undertaken has included the manufacture and installation, replacement or overhaul of a wide range of equipment including propellers, propeller shafts, steering gear, rudders, gearboxes, motors, bearings and stabilisers.