Alex Carey top-scored as Australia's batting woes continued - being bowled out for 231 by South Africa in Friday's one-dayer in Adelaide.
The Australians were all out in 48.3 overs - the seventh time in their past eight one-day internationals they have failed to bat their allotted overs.
Carey made 47 from 72 balls, Chris Lynn struck 44 from 44 deliveries and captain
Aaron Finch made 41 from 63 balls.
Proteas paceman Dwaine Pretorius took 3-32 from 10 overs while Kagiso Rabada(3-53) and Dale Steyn (2-31) also claimed multiple wickets.
South Africa, seeking a win to take an unassailable 2-0 lead in the three-matchseries, put the brakes on just as Australia appeared set to accelerate.
Lynn's knock featured three fours and two sixes but he fell when hitting top gear.
The Queenslander had smacked 18 runs from four consecutive Rabada balls - a six followed by three fours - but was out next ball.
His dismissal continued a trend as Australia's batsmen formed a series of handy stands without converting any into imposing totals.
Finch put on 30 runs with Lynn before the skipper departed, chopping a short ball from Pretorius onto his stumps.
Lynn and Carey then added 37 runs before momentum again stalled with Lynn's dismissal.
South Africa soon captured the wickets of Glenn Maxwell, Marcus Stoinis, Pat Cummins, Mitchell Starc and Carey.
Spinner Adam Zampa added a late flourish, making 22 from 24 balls and putting on 27 runs for the last wicket with Josh Hazlewood.