Harwell made all eight of his free throws and Colvin all nine of his while Keith Smith adding 16 points while going 8 of 10 from the line. The Mustangs were 36 of 41 from the stripe, including 31 of 35 in the second half.
Vanguard made seven more baskets, including one more 3-pointer, but made only 18 of 27 free throws. Isaiah Gentry led the Lions with 20 points, making all nine of his free throws.
Cal Poly held the lead entire second half with an 8-0 run giving it a 80-68 advantage with just under two minutes left. The Lions cut their deficit to two with 19 seconds left but the Mustangs got a free throw from Keith Smith before the Lions missed two 3-point tries in the final seconds.
The Mustangs (3-11) snapped a four-game losing streak and are hosts to UC Santa Barbara on Wednesday.
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