Despite the loss, Island Park remains in third position with seven points and is 13.5 games ahead of Otago Gold, Chisholm Links and North Otago.
The top Balmacewen team owes its elevation to Otago Gold (B team) which held St Clair to 3-3 at St Clair on Saturday, leaving the leader with a single point.
At the halfway stage, Otago Blue's Nick Borren is the star of the series with four wins from four outings while Michael (Moxy) Smith is unbeaten with three wins from three matches. Chisholm's Cody McMullan has four wins and one loss.
Jeremy Morgan (Otago Gold) and Kyle Geary (Chisholm Links) are also unbeaten with three wins but individual results show St Clair is still in the driving seat.
Brent McEwan, Chris Snow and Tony Giles are all unbeaten with three wins while Stephen Hitchcox has won both his games this year.
For St Clair, Jacob Bellamy and Giles posted convincing 5 and 4 wins while No1 Ryan Bellamy accounted for Otago Gold's Ben Turner with one hole to spare.
However, St Clair lost the initiative when Gold No2 John McIntee and No3 Jeremy Morgan won with good margins.
No5 Jakob Bleach had difficulty on the greens coming home gifting the deciding match to Balmacewen's Murray Edgar on the final green.
The Chisholm Links sextet was always in control in its 4.5-1.5 win over North Otago.
Kyle Geary, Cody McMullan, captain Mark Collie and Ben Butler got home with holes to spare while Oamaru's Cameron Ryder downed Matthew Heaton on the 14th green.
The closest and most exciting game was between masters (over-40) triallists Sean Geary and Gary Creedy which ended in a tie.
The top two Otago Blue players Nick Borren and Brandon Hodgson had comfortable wins beating Island Park's Jarden Hammond and Monty Wong in 13 holes.
Ben Patston and Jason Hughes posted 2 and 1 wins while last weekend's hero, Michael Wray, won Island Park's only game at the expense of Daniel Elder.
The battle between the No6 golfers went the full distance on flooded greens with Luke Murdoch and Logan Green finishing all square.
