San Diego, which trailed 38-28 at the half, pulled within 63-61 with 1:29 left on Chris Sarbaugh's 3-pointer but Mornar answered with a three-point play. From there the Toreros had a turnover and five straight misses.
Evan Payne added 19 points for the Lions (8-16, 4-8 West Coast Conference), who shot 54.5 percent, including 7 of 15 3-pointers, and made 15 of 20 free throws. Mornar, who had 20 points at halftime, was 11 of 12 from the line.
Johnny Dee hit 10 of 14 shots, including 5 of 9 from 3-point range, to lead San Diego (12-12, 5-7), which had its three-game winning streak snapped. Dee hit all four of his free throws to run his streak to 36. Brand Parry added 16 points.