McMahon was the driving force as the Cavaliers defeated Wheeling Jesuit, 18-8, for a big win to open the conference schedule.
The junior attack produced five goals and two assists in the home win as Walsh outshot the Cardinals, 35-33.
McMahon scored four times alone in the second period, including three straight goals in about a three-minute span that helped give his team an 11-7 lead at halftime.
McMahon scored the lone goal in the third period and then as Walsh had a 6-1 edge in the fourth period, he provided an assist.
McMahon now has 11 points (8 G, 3 A) in six games played this spring. He has taken 16 shots and made five starts.