Robbie Knapp was 4-for-5 with three RBI and Brandon Cohen was 2-for-4 with his third home run of the season, in front of a sellout crowd of 3,279 at Road Ranger Stadium.
The RiverHawks, who have won a season-best six in a row, took sole possession of the last of four Frontier League playoff spots with eight games left. Traverse City lost, 3-1, to Florence and the slumping Beach Bums dropped out of a three-way tie for the wild-card spot with their fifth loss in a row. Gateway, which entered the day tied for the wild card with Rockford and Traverse City, lost, 6-5, in 12 innings at River City.
McTamney escaped a two-on, two-out jam in the second inning with a strikeout of Chris Crescenzi. McTamney went on to retire 10 in a row, including a strikeout of the side in the fifth inning. McTamney (4-1) scattered five hits and did not walk a batter in the victory.