After languishing in fifth place with four points and 12.5 games at the halfway stage of the series, the defending champion has rocketed into second place with 13 points and 26.5 games.
Ryan Bellamy, Michael Ormandy, Chris Snow and Stephen Hitchcox all posted wins for St Clair, ensuring the Corstorphine golfers won the fixture.
Jacob Ormandy made a birdie three on the final hole to beat Matthew Heaton, giving his team a fifth win to ensure second place.
But in a massive fightback, No6 Greg Johnson was five down with five holes to play, winning the final five holes to square his match with Peter Rae and put the icing on the cake for St Clair.
Otago Blue continues to lead the series with 19 points and 30 games after beating Island Park on the Waldronville course 4-2 on Saturday.
But the Balmacewen golfers had to come from behind after looking set to post a draw with Island Park at the turn.
Pen Patston, Jason Hughes and Brandon Hodgson all won for Otago, while Island Park No4 Andrew Hobbs coasted home, beating Tyrone Ratahi in 15 holes.
Otago No3 Nick Borren was four behind Park captain Michael Minty at the turn but birdied 10, 11 and 12 before eagling 13 to get back to a deficit of one.
However, Minty stayed in front, finishing the match in his favour by winning the par 4 17th hole.
No1 Michael Smith was four down to Monty Wong after seven holes before winning eight and nine and losing the 10th to get back to three down. But with several birdies, Smith won six of the next seven holes to post Otago's fourth win by 3 and 1 on the penultimate green.
In a clash of the cellar-dwellers, Otago Gold posted its first win, beating the second St Clair team by a 4 to 2 margin.
It looked like being tied 3-3 until Otago No1 John McIntee beat Simon Murley on the final green, giving the Balmacewen B team its first win in the series.
McIntee, Ben Turner, Paul Hubbard and Murray Edgar all won for Otago, while Tony Giles had a convincing 5 and 3 win at the expense of Scott Clark.
The champagne corks were popping after St Clair's Ross Colquhoun beat Joseph Hancock for his first win this year, having previously halved five of his games.
