Western Illinois was just 5 of 26 in the second half (19.2 percent), including 0 for 7 from 3-point range.
Matt Kavanaugh and Paul Williams added 15 points each for the Flyers, and Josh Parker chipped in 11 points. Chris Johnson tallied 10 points for the Flyers, who have won six consecutive season openers.
Dayton scored 20 points off 16 Western Illinois' turnovers, and kept the Leathernecks in the half-court game, as they were outscored 13-0 on fast breaks.
Obi Emegano and Tommie Tyler led the Leathernecks with 15 points.