The Harbour forward pack set the foundation for a victory over Green Island at Miller Park.
The Harbour pack was again inspired by captain Peter Mirielees, who, along with prop Greg Restieaux and lock Norris Goldberg, played a key role in a strong first-half performance.
When Pieter Van der Merwe and Sam Ready replaced Restieaux and David Kahukiwa in the second spell, it only served to compound Green Island's woes at the set piece.
Goldberg was quick to the breakdown and complemented solid work by flankers Dalton Ellis and Angus Duckett, with both Goldberg and Ellis winning clean ball at the lineout.
The work up front was backed by a solid display at halfback by Dan Smart, who scored two tries.
His passing was sharp and assured and his interaction with first five-eighth Olly Cuthill provided plenty of spark to the outside backs.
Lex Kaleca and Corey Kara were solid in defence while, at the back, Ben Main and Craig Sneddon were dangerous on the counter-attack.
Green Island did not take a backward step. Its three tries came from sharp backline moves, while featuring up front were Jason Bint, Mika Mafi and Simon McCarthy.
- Harbour 35 (Dan Smart 2, Peter Mirielees, Lex Kaleca tries; Craig Sneddon 3 con, 3 pen), Green Island 18 (Sam Eriepa, Jared Fahey, Jesse Toto tries; Jared Fahey pen). Halftime: Harbour 23-8. Referee: Gareth Reed.