It really was death by scrum for Dunedin. The Sharks could not match Southern's power up front.
Harbour is also unbeaten after three games. It was too good for Zingari-Richmond, running in eight tries to win 54-17 at Montecillo.
At Miller Park, Green Island continued its promising start to the season. It beat Kaikorai 43-29. The Grizzlies defended for most of the first half but broke out with five second-half tries.
In the other game, Taieri beat Alhambra-Union 43-20 in an entertaining match at Peter Johnstone Park.