Martin Maldonado's two-run double was the key to a three-run Milwaukee fourth that put the Brewers in front and they then broke it open with five runs in the fifth.
Jean Segura singled and Carlos Gomez and Khris Davis both walked to load the bases in the fifth before Betancourt hit his 13th home run of the season. Norichika added an RBI single later in the inning for a 10-2 lead.
Kyle Lohse (8-7) received 11 hits of support and held the Mariners to three runs on six hits in seven innings to get the win.
Milwaukee roughed up Joe Saunders (10-11) for four runs on seven hits in 4 1/3 innings.