Manawatu led 8-6 until another Walker penalty edged Harbour back in front 9-8 with less than two minutes remaining.
North Harbour had conceded 17 tries in four games going into today's match and once again looked half a pace too slow on defence.
There was nothing wrong with their attack, however, and a superb team try right on the halftime whistle to winger David Raikuna gave them a 14-8 lead at the break.
Started by winger Nafi Tuitavake, and boosted with a mazy run from captain and halfback Chris Smylie, sublime handling at speed led to a precision finish from Raikuna.
Manawatu worked their way back into the game, reclaiming the lead 15-14 with just on 20 minutes to go.
They built pressure phase after phase, finally spinning the ball wide to winger Tomasi Cama, with quick hands from Milne-Skudder at the final pass sending the sevens star over in the corner 14 minutes into the second half.
Cama underlined his versatility with a dropped goal seven minutes later to give Manawatu a four-point lead.
Harbour's fragile defence was again exposed in the 67th minute as Cama's initial break was finished clinically by halfback Aaron Smith. Cruden's conversion gave the home team a 25-14 lead, and Harbour looked out of ideas.
However, with 10 minutes left Walker pulled one back for Harbour after a strong burst through the midfield from replacement loose forward Irwin Finau.
No 8 Matt Luamanu came close before Walker scooped up the loose ball to dive over. Ben Botica sank the conversion to narrow Manawatu's lead to four, but the visitors never really threatened the line again.
And another Harbour defensive muddle in injury time gifted Manawatu the bonus try, an opportunistic effort from Cruden which he then converted.
- NZPA