Rockingham are the first team into the Dudley Tuckey Cup grand final in a fortnights time.
The Rams were too good for South Mandurah in the second-semi final claiming a 11.13.79 to 7.l7.49 triumph.
Centrals are out of the finals race after losing to Baldivis in the knockout first semi-final 10.11.71 to 9.7.61.
Souths and Baldivis will meet in the preliminary final next Sunday. It is expected the games will be held at Mundijong Oval.
Earlier in the day Rockingham had qualified their reserves and colts straight into the grand final with victories.
PRELIMINARY FINAL FIXTURES:
League - South Mandurah v Baldivis 2:30PM
Reserves - Baldivis v South Mandurah 12:30PM
Colts - South Mandurah v Halls Head 10:20AM