Dartmouth (8-2, 6-1) ran up 518 yards of offense and limited Princeton (5-5, 4-3) to 228.
Bo Patterson hauled in three of Williams' scoring strikes, with catches of 58, 38 and 12 yards. Patterson finished with five receptions for 129 yards.
Williams hooked up with Patterson on the fourth play of the game, a 58-yard catch-and-run, to set the tone for the day. Princeton responded with an 11-play, 44-yard drive culminated by Nolan Bieck's 46-yard field goal to make it 7-3, but that's the closest the score was all day.
The Big Green rolled off 34 unanswered points to push the lead to 41-3 midway through the fourth before the Tigers dented the scoreboard again on Joe Rhattigan's 1-yard plunge late in the game.