Powerful centre Wayne Gibson used his strength to score a hat trick of tries when Harbour beat Alhambra-Union at Watson Park.
The pack dominated the first spell and took two tightheads that were exploited by efficient halfback Johnny Legg, who kept the momentum with Harbour.
A try by hard-working second five-eighth Lex Kaleca just before the break gave Harbour a decisive 21-6 lead at the break.
Alhambra-Union came back strongly early in the second spell and reduced the gap. But this was answered by Harbour with tries after nine and 18 minutes that made the game safe.
Flanker Angus Duckett was efficient at the breakdown and mobile around the paddock and locks Nick Harwood and Sam Ready contributed to Harbour's win.
Lock Matt Kissick led by example and was the best of the Alhambra-Union forwards. First five-eighth Peter Breen kicked four goals but lacked decisiveness in general play.
The Harbour pressure led to too many errors and the Alhambra-Union backs dropped too many passes.
Harbour 38 (Wayne Gibson 3, Lex Kaleca, Nick Harwood tries; Ollie Cuthill 2 con, 3 pen), Alhambra-Union 25 (Tili Puloka, Chris Guild, Nick Wright tries; Peter Breen 2 con, 2 pen). Halftime: 21-6.
