The defeat left Harbour languishing in sixth on the Championship standings, a disappointing reality given the visitors were initially more clinical in the right areas to take a slight edge to the break.
While Manawatu was struggling with their set piece, Harbour struck through Josh Rowland after a well-worked scrum move, receiving reward for their dominance.
But the setback seemed to spark Manawatu to life, with Fraser Stone helping the home side almost immediately strike back. And the Turbos continued to find fluency after the break, aided by ill-discipline and poor handling from their opponents.
Harbour were dangerous when they did hold onto the ball, with a flowing backline move allowing Matt McGahan to score his side's second. But falling further behind again seemed to spur the Turbos, with Nathan Tudreu's bruising run enabling Callum Gibbins to cross.
And Manawatu soon found the lead through Newtown Tudreu, capitalising on Otere Black's pinpoint cross kick, before Gibbins' second grabbed the bonus point.
Manawatu 31 (F. Stone, C. Gibbins 2, Newton Tudreu tries; O. Black 4 cons, pen)
North Harbour 17 (J. Rowland, M. McGahan tries; B. Hall pen, 2 cons)
HT: 7-10