South Perth notched a 26-16 victory over North Beach in a fiery clash of the WA Rugby League top two at Charles Riley Reserve on Saturday.
Tempers boiled over with four players either sin-binned or reported as the match neared half-time.
The win gave South Perth a final series berth for the Lions who have a bye at the weekend.
Willagee staked their claim for a finals spot with a 52-8 demolition of cellar-dwellers Kalamunda Bulldogs at Weber Reserve.
Fremantle, 52-12 winners over Joondalup, move to fourth in a log-jam where just five points separate second and fifth.
1. South Perth 29
2. North Beach 21
3. Willagee 20
4. Fremantle 18
5. Joondalup 16
6. Rockingham 12
7. Kalamunda 9