The Dons (11-9, 5-5 West Coast Conference) have won consecutive games since snapping a three-game skid. Portland (9-14, 3-7) has lost three straight and seven of its last eight games.
Dont'e Reynolds chipped in 12 points and grabbed 13 rebounds for San Francisco, which had six in double-figure scoring.
San Francisco had a 51-45 halftime lead, and opened the second half on a 12-4 spurt to stretch its lead to 63-49. Boyce and Reynolds scored four points apiece, and the Pilots missed 7 of 9 shots during the span.
Tyson scored six straight points to pull the Pilots to 79-74 with two minutes left. Uche Ofoegbu converted a 3-point play, and the Dons made 5 of 6 free throws to seal it.