Bell made 5-of-6 from long range in the opening half, pushing Gonzaga to a 46-18 lead at the break. His five 3-pointers were only one point less than Marymount's entire field goal total in the opening 20 minutes.
Gonzaga won for the 12th time in 13 games and remained the only unbeaten team in West Coast Conference play.
Bell scored all of his 15 points in the first half and Kelly Olynyk had 15 as well. The Bulldogs improved to 20-2 and to 7-0 in conference play. Gonzaga wound up hitting 13-of-20 from beyond the arc.
Anthony Ireland scored 19 points for Marymount (8-13, 1-7)