Saint Mary's took control with an 18-0 burst, extending a one-point lead to 60-41. Carter hit back-to-back 3-pointers and Waldow capped the run with 8:19 left. The Gaels (20-6, 12-3 West Coast) went 7 for 9 from the field during that stretch and 14 for 22 in the second half.
Thomas van der Mars had 17 points and 10 rebounds for Portland (16-11, 7-8), which lost its ninth straight to the Gaels.
Saint Mary's will retire the jersey of Patty Mills (2007-09) in a halftime ceremony on Saturday when it hosts No. 3 Gonzaga.