With plenty of possession and a mountain of territory, Otago struggled to get any momentum in its game, and led just 10-5 halfway through the second half.
But it put the pedal down in the final quarter and scored three tries in the last 20 minutes to take a bonus point at the University of Otago Oval.
Sheree Hume, who started at fullback and moved into first five-eighth, was the impetus to guide the home side to victory.
She spotted a gap in the Harbour defence off a maul and with a nice piece of acceleration and step, scored under the posts. That gave the Spirit side a 17-6 lead and also some extra confidence. Shortly afterwards, replacement outside back Cheyenne Cunningham was on the end of a sweeping 80m move which had Spirit players running nice angles and off-loading well.
The bonus point was sealed when replacement winger Kiana Wereta went over in the corner after the Harbour defence ran out of numbers with two minutes left. Harbour scored in the last movement of the game.
Otago coach Scott Manson said it was good to get the win and the side had kept it shape well in both attack and defence.
"But our turnovers killed us. I think we had like 13 in the first half and our accuracy really let us down. But we hung in there and played better in the second half," he said.
"I though the lineout was really good and the bench in the second half made a real difference. A lot of sides I’ve been involved with don’t have the strength on the bench but this team does. The players that came on did really well."
The Spirit had a monopoly of ball and territory in the back end of the first half. It camped inside the North Harbour 22m line, but rather rushed things and could not get over the line.
Manson said the side was trying to score too quickly and lacked accuracy at vital times.
It could not hang on to the ball while North Harbour scrambled well on defence.
Otago’s only try in the first half came from midfielder Greer Muir, who ran a nice line off a scrum to barge over.
The home team was tenacious in the breakdown, and flankers Morgan Henderson and Georgia Mason worked hard to get their hands on the ball.
Halfback Sammy Wong threw some good passes, while in addition to the impressive Hume, Muir ran hard when she had the ball.
North Harbour rather ran out of ideas the longer the game went on, and bodies tired. Its locks Sophie Fisher and Rebecca Wood were instrumental in the North Harbour effort, with Fisher displaying an educated right boot.
The Spirit is at home again this Saturday when it takes on Hawke’s Bay.
Farah Palmer Cup
The scores
Otago Spirit 27
Greer Muir, Sheree Hume, Cheyenne Cunningham, Kiana Wereta tries; Hume con, pen; Rosie Kelly con
North Harbour 13
Finesa Makasini try; Sophie Fisher 2 pen, con
Halftime: 7-6 Otago