Bailed out by the brilliance of Joey Manu, New Zealand coach Michael Maguire says his side must fix up their act sharpish after scraping into a Rugby League World Cup semi-final with Australia following an unconvincing 24-18 win over Fiji.

It took until the 70th minute in Hull on Saturday for Maguire's side to hit the lead after an underwhelming showing which would have done little to worry Mal Meninga's Kangaroos.

The tightness of the game brought back memories of the 2017 quarter-final when the Kiwis were knocked out by Fiji at the same stage, costing then-coach David Kidwell his job.

But this time Maguire's men were saved by the mercurial abilities of Manu.

The fullback, who was named man of the match and clocked over 300 metres with the ball in hand, got them out of jail by scoring the try which drew them level at 18-18.

He then won the penalty goal which helped them hit the lead, before a late Jordan Rapana try sealed the victory and booked them a place in the semi-finals at Elland Road on Friday.

"We need to get better and the start, they jumped us and you can't do that."

The win puts Manu on a collision course with Sydney Roosters teammate James Tedesco, who appears his closest rival for the Golden Boot.

"He (Manu) did a great job for us and I think he's learning a little bit about the players around him too," Maguire said.

"It's probably the third game that we've had our spine all together, so we'll be better again on the back of that."