Preston Mattingly added career highs of 16 rebounds and 11 points for his first double-double.
Leading 30-27, Lamar's Nick Garth scored five points to begin a 15-6 run to open the second half, and Sears had seven straight points in a 12-0 stretch for a 58-40 lead with 7:53 remaining. Jarvis Christian trailed by 13 before a 12-2 run left Lamar ahead 76-53 with 1:53 to go.
The Cardinals (6-4) committed 10 of their 15 turnovers in the first half and Jarvis Christian led 11-4 before Sears scored seven points in a 9-0 spurt. Trailing 16-15, Lincoln Davis scored five straight points to put Lamar ahead for good.
The NAIA Bulldogs (1-10) were led by James Parker with 11 points.
The victory was the 300th for the Cardinals in Montagne Center.