Harbour edged University 10-5 in an arm wrestle at the University of Otago Oval this afternoon.
Both sides blew opportunities to score more points but some of the defence was brutal and both packs will be be nursing bruises.
Green Island consolidated its spot at the top of the competition standings with a 68-14 win against Zingari-Richmond at Miller Park.
The Grizzlies remain undefeated with four bonus-point wins in a row.
Kaikorai did the basics well against a misfiring Alhambra-Union at the North Ground. The 38-22 win lifts it into second place.
Southern upset Dunedin 32-10 at Bathgate Park to register its second win.
The scores:
Green Island 68-14 Zingari fulltime
Alhambra Union 22-38 Kaikorai fulltime
University 5-10 Harbour fulltime
Southern 32-10 Dunedin fulltime