McMahon (16) displayed sensational early championship form over the opening three days of competition winning six finals — 200m freestyle, 200m butterfly, 50m breaststroke, 400m individual medley, 100m breaststroke and the 400m freestyle.
McMahon added to her haul yesterday, with victories in the 200m individual medley and the 50m freestyle before claiming her final medal — and setting an Irish Junior record — in the 100m butterfly.
Dubliner Niall Wynn continued his impressive form, taking the 200m individual medley from close rival Johnny Quinn.
Nicholas Quinn won the 200m breaststroke and earned breaststroke final in 2.20.65, a time which secured him qualification for the European Junior Championships in Serbia.
Phillip Duffy swam within 1% of the qualifying standard for the Juniors in the 100m butterfly final (55.95) meaning he will also be considered for Serbia.
Other winners included Catriona English (Aer Lingus) in the 200m breaststroke and Botond Solymossy (Westwood) in the 50m freestyle.
On Saturday, Melanie Nocher won the 200m backstroke final (2.12.73) which secured her place on the Irish squad for July’s World Championships in Shanghai by taking the 200m backstroke crown.