With wind and rain throughout the day, scoring was so difficult that the CSS rose to 78 reduction only.
Johnston's performance in the conditions was admirable, returning a scratch score of 75 to win the trophy by four strokes from his nearest challenger.
Leading Scores :-
75 - James Johnston (Ayr Belleisle)
79 - C McFarlane (Irvine)
80 - Matthew Dargie (Royal Troon), Sandy Buchanan (Prestwick St Nicholas),
Colin McGowan (Troon Welbeck)
81 - Gary Jordan (Crosshouse), Bruce Caldow (Kilmarnock Barassie)