Powerful centre Siaosi Folau was in blockbusting form as Harbour comprehensively beat Green Island at windswept Watson Park.
Folau's powerful running from centre yielded him two tries and he was the fulcrum of many Harbour attacks.
Harbour played textbook rugby into a howling southerly to lead 22-0 at halftime, attacking Green Island through the middle and at close range around the fringes with good ball control.
But it lost its momentum in the second spell when it was too ambitious in the wind and long cut-out passes were either dropped or floated out of control.
Green Island's defence also tightened and it deserved a consolation try as it hammered away on attack for the last 10 minutes.
Johnny Legg controlled play intelligently at halfback for Harbour, Luke Shervey was outstanding on attack and defence from the blindside flank, Brad Griffiths was an industrious No 8, lock Graham Cashmore did excellent work in the line-outs and Peter Mirrieless was a combative hooker.
It was a fruitless day for Green Island but it never stopped trying.
Paul Butson was useful, first at halfback and later at first five-eighth, prop Andre Clark was unyielding in his efforts and hooker Frankie Elisara tried hard in his 100th game.
Harbour 27 (Siaosi Folau, 2, Iloa Lihau, Sam Ready tries; Craig Sneddon 2 conversions, penalty goal), Green Island 0.
Referee: Ross Barnett.
Halftime: Harbour 22-0.
