Ohio Wesleyan will face Robert Morris (Ill.) in the tournament championship game on Sunday. Robert Morris defeated Hanover, 87-79, in Saturday's other first-round game.
King's first pair of 3-pointers gave Ohio Wesleyan a 12-6 lead with 15:37 to play.
The Purple Raiders closed to within 12-10 on baskets by Kyle Karpinski and Matt Ferguson, but Ohio Wesleyan answered with baskets by junior guard Matt Shirer and King and a pair of free throws by junior wing Ted Uritus to take an 18-10 lead.
Karpinski led another Mount Union comeback, draining a pair of free throws and converting a 3-point play to highlight a 7-0 run that sliced the Ohio Wesleyan lead to 21-19 with 8:52 left.
Ohio Wesleyan answered with its 14-2 run that included King's pair of 3-pointers and a 3-pointer by senior wing Andy Warnock. The spurt gave the Bishops a 35-21 lead with 5:46 left in the first half.
The Purple Raiders came within 38-31 at halftime and closed to within 38-34 on L.J. Helton's 3-pointer to open the second half, but Ohio Wesleyan had an answer for every Mount Union surge.
The closest Mount Union would come was when Karpinski's bucket with 5:51 left brought the Purple Raiders within 56-53, but junior post Ben Chojnacki, Warnock and sophomore post Dustin Rudegeair scored baskets to increase the Bishop lead to 65-57 with 3:32 to go.
Mount Union rallied to within 70-66 on Eric Fender's 3-pointer with :41 to go, but Ohio Wesleyan sealed the game as senior guard Ross Rybarczyk went 4-for-4 from the line in the closing seconds.
King led the Bishops with 24 points, including a 7-for-10 shooting performance from beyond the arc. Chojnacki added 19 points, going 8-for-8 from the field, and Rudegeair added 11 points and a team-high 7 rebounds. Rybarczyk led the Bishops with 3 assists.
Karpinski led Mount Union with 35 points and 5 rebounds. Fender finished with 10 points and shared the team lead with 4 assists. Helton also contributed 4 assists.