Matthew Dellavedova added 11 points and six assists for the Gaels (15-4, 4-1 West Coast), who never trailed.
St. Mary's held Portland to 43 points in the schools' previous meeting, on Feb. 23, 2012.
Paul McCoy made his long-delayed debut with Saint Mary's, with one rebound in three minutes.
The senior guard and Portland native transferred from SMU after the 2009-10 season, sat out the following year per NCAA rules, then missed all of last season after suffering a second knee ACL tear. He averaged 13.4 points as an SMU freshman in 2009-09.
Thurl Bailey, a member of the 1983 NC State title team, has helped get the Wolfpack an invitation to the White House to meet President Barack Obama on May 9.
It's about time for someone other than Duke and Kentucky to grab the top class. Could it be Shaka Smart and Texas in 2017?
Which teams have enjoyed the most NCAA tournament success since 2000? Kansas' recent run to the Elite Eight vaulted the Jayhawks up the list.