They're the Illawarra Premier League's very own Jekyll and Hyde - brilliant one week, disappointing the next.

Two weeks ago, Wollongong Olympic sent shockwaves around the league with a 5-0 demolition of defending premiers Port Kembla.

On Sunday, they suffered their second straight mauling.

South Coast United punished the visitors 3-0 at Ian McLennan Park to leave Olympic coach Wayne Farnsworth baffled by his squad's topsy-turvey displays.

"We are not getting out of the blocks. Last week, they didn't turn up at all in the first half and the game was gone and it was pretty much the same today," Farnsworth said.

"It is frustrating, we certainly need to get consistency."

To South Coast's credit, they were clinical in the opening stanza, capitalising twice from set-pieces and once on the break to move out to an almost unassailable advantage before half-time.

Andrew Paine got the first of his two goals with less than 10 minutes played, curling an effort just inside the post before adding his second with a bullet strike from a corner in the 40th minute.

It was curtains five minutes later when Olympic were again caught napping from the dead ball situation, as Anton Batur flicked on a header into the back of the net.

Farnsworth had seen enough at half-time and made all three of his changes during the break to try to reinvigorate his side.

He saw immediate results as the visitors finally started playing the football the gaffer had hoped for.

But it all came undone before it could truly prosper when Gavin O'Brien selfishly got himself sent off.

Shortly after being involved in an exchange which had the United faithful calling for a red card, the midfielder gave the referee no choice with a challenge that wouldn't have looked out of place on a rugby pitch.

Following his dismissal, South Coast had a number of chances to score again yet Olympic also looked threatening but there was no change to the score.

"We haven't been scoring many goals, so three goals is good for us," South Coast coach coach Alan Paine said.

"Another clean sheet - we have only had four scored against us all year.

" Everywhere we play we put in a monster effort and that was on show again," he said.

In Sunday's other match, Sam Munro's late goal helped Dapto Dandaloo Fury remain undefeated via a 2-1 result against Port Kembla.