Bad weather at sea has set back the expected arrival of the first new railway locomotive engines to be imported into New Zealand for more than 30 years.

What the first new locomotives to arrive in New Zealand in 35 years look like.

The freighter Beluga Foresight, which is carrying the first six of KiwiRail's 20 new DL class locomotives, has missed the morning tide for Friday and is now expected alongside at the Port of Tauranga mid afternoon that day.

'It has been working its way around a tropical storm for the last few days,” says Kiwirail public affairs manager Jenni Austin, 'but it is heading in the same direction as the storm.”

Expected rain over the weekend could further delay discharge of the locomotives, which Jenni says is now expected on Sunday at the earliest.

Once ashore, the 108 tonne locomotives will be unwrapped at Mount Maunganui and prepared for a tow to Te Rapa for commissioning.

They are expected to be operating between Auckland, Hamilton and Tauranga before Christmas. The remaining 14 in the NZ$80 million purchase are due early next year.

The double-cab diesel-electric DLs produce 2700kW or 3621hp at 1800rpm from German MTU 20V engines. The 4000 series R43 are a fuel efficient, turbocharged common rail injected engine that meets tough European emission standards.

The DL's pulling power is similar pulling power to the 4000hp EF electric locomotives built in 1988 for the electrified sections of the North Island Main Trunk.

They will be the most powerful diesel electric locomotives on KiwiRail tracks.

'These locomotives and subsequent additions to our wagon and locomotive fleets will play a critical role in KiwiRail's Turn Around Plan – the 10-year programme to create a sustainable rail business that can stand on its own feet financially,” says Jenni Austin.

'The government commitment to funding these 20 new locomotives and further investment in additional rolling stock over the next three years will enable considerable efficiency and capacity gains on key freight routes.”

KiwiRail operates 149 mainline locomotives, the newest of which are the 17, 4000hp EF locomotives built for the electrified section of the North Island Main Trunk in 1988.