Game two will be played at Phil Welch Stadium on Thursday. A Mustangs win would force a decisive championship game in St. Joseph on Friday.
St. Joseph struck first thanks to a triple by Kyle Richards that plated Tanner Lubach and Brandon Huske.
Starter Ryker Fox kept Sedalia off the board until a three-run fourth inning. Jordan Dey plated Trey Hair and Alex Bee to tied it before Huter Leeper scored on an error by Huske.
The Bombers added a run in the fifth and seventh innings to hold off any Mustang rally.
Fox allowed all five runs on nine hits over six innings. He struck out five batters.
Joe Koerper tallied St. Joseph's only other score by grounding into a fielder's choice in the seventh.
Dan Chambliss got the win after pitching 6 1/3 innings of relief. Starter Cole Bartlett left the game in the second after hearing a pop in his elbow. He struck out four of the first five batters he faced.
First pitch from Phil Welch Stadium on Thursday is 7 p.m.