Harbour scored two late tries in the first half to set up an 18-12 win against Southern at Bathgate Park.
The Hawks led 18-9 at the break and produced a wonderful defensive effort to repel Southern.
University withstood a second half resurgence from Taieri to bank a 22-14 win at the University Oval No 6 ground.
Dunedin thumped Green Island 40-5 at Miller Park and Kaikorai dispatched Zingari-Richmond 27-7 at Bishopscourt No 3.