Green Island finished the stronger to gain a surprise but deserved bonus-point win over Harbour at Watson Park.
Green Island battled back from a 5-14 deficit to play much better in the last hour and score four tries to four as it clinched its second win of the season.
Harbour started well but lost its way as the match progressed.
Its cause was not helped by it being hammered in the penalty count.
The game was still in the balance at 22-20 with four minutes left but Hanipale Galo made a scorching break down the right wing and first five-eighth Sam Eriepa was in support to take the pass and score the match-clinching try.
Centre Corey Kara and lock Sam Ready scored tries in the first quarter as Harbour built a handy lead but mistakes crept into its game, the penalty count increased and Green Island came back at it. Kara was sin-binned for a professional foul near the end of the first half.
Green Island tightened its defence, seized its chances on attack and outscored Harbour 15-6 in the second spell.
Flanker Scott Higginson was a towering figure for Green Island, in the tight-loose and lineouts, and No 8 Josh Beer was almost as good as the Green Island pack warmed to its work. Big centre Roma Sauliego scored one blockbusting try and had a handy all-round game.
First five-eighth Lance Taylor was neat and tidy for Harbour and the front row of Peter Mirrielees, Ben Nolan and Pieter van der Merwe outscrummed its opponent but the combination between backs and forwards was lacking.
- Green Island 27 (Scott Higginson, Josh Beer, Roma Saulioge, Sam Eriepa tries, Saulioge 2 con, pen), Harbour 20 (Corey Kara, Sam Ready tries, Lance Taylor 2 con, 2 pen). Halftime: Harbour 14-12. Referee: Adam Morrison.