The Mustangs (35-14, 24-13 MINK) took advantage of miscues by the Mudcats (27-15, 24-15 MINK) sparking a five-run third inning in the opening contest.
Hayden Steele reached on an error, Lucas Powers walked and Ryan Abernathy singled to fill the bases. Trent Hill followed with a bases loaded walk to force in the first run of the inning.
Joe Koerper and Mike Sherburne added RBI singles, and Kyle Richards delivered the final blow driving in two on a double.
The offensive outburst gave Dixon Marble all the run support he needed.
The St. Joe starting pitcher allowed two runs in the first, but limited Chillicothe to one in his final four innings of work. Marble nabbed his first win of the summer while recording a season-low one strikeout.
Hill tossed two scoreless innings to pick up his first save in St. Joseph.
The Mustangs sent Jake Jones and his stellar 0.32 ERA to the mound in game two, but he gave up a season-high six runs -- four earned -- in 6 1/3 innings.
Chilli's Todd Czinege cranked a three-run home run off Jones in the third anchoring the Mudcats to a 4-0 lead.
St. Joe got a pair back in the fourth off a two-run single from Zac Johnson, and they tied it with two more in the fifth.
The Mudcats broke the tie in the top of the seventh with some assistance from the Mustangs.
After an error loaded the bases, Chillicothe scored the go-ahead run on a catcher obstruction call. Two more scored on a fielder's choice to put the game out of reach.
Two of St. Joe's final seven games come against Chilli. The North Division rivals play a doubleheader Sunday at Chillicothe.