Harbour ran rampant in the second spell to overwhelm Pirates in muddy conditions at Watson Park.
Harbour, bottom of the competition when the round began, moved off the foot of the table as it scored six tries to one.
The victory came off the back of a dominant tight five, in which lock Hale T-Pole and hooker Peter Mirrielees were outstanding, and some fine counterattacking by the backs.
Fullback Ollie Cuthill contributed 20 points, including six goals, while No 8 Hadley May scored a hat trick of tries on the wing in the final quarter as Harbour rammed home its dominance.
T-Pole, who will play for Northland this season, was the outstanding forward of the game with some barnstorming runs in the tight-loose, but it was a fine overall display by the pack.
Sam Ready was an honest contributor as T-Pole's second-row partner, while loosies May, Eben Joubert and Scott Fuglistaller benefited from the amount of go-forward possession.
Halfback Johnny Legg revelled in the muddy, slippery conditions and there was some strong running out wide by Lex Kaleca, Wayne Gibson and George Folau.
Pirates started well and scored the first try but it did not help its cause with some poor kicking which enabled the Harbour backs the time and space to launch counter-attacks.
Flanker Josh Clark, in his 100th game, tried hard throughout, while Kieran Fowler was safe at fullback and looked likely on attack but the backs had little quality ball to play with.
Harbour 45 (Ollie Cuthill, Johnny Legg, Hale T-Pole, Hadley May 3 tries; Cuthill 3 con, 3 pen), Pirates 5 (Poamo Aiiloilo try). Halftime: 16-5.