Iona hit 54 percent from the floor, including 13 of 27 from beyond the arc. Leading scorer Sean Armand was held to just 11 points.
Siena (7-12, 3-5 Metro Atlantic) trailed by six points midway through the second half when A.J. English's layup kicked-off an 11-2 Iona run capped by a Williams layup giving the Gaels a 70-57 lead with seven minutes to play.
Tavon Sledge's basket inside the paint extended Iona's lead to 17 with 4:40 left, marking the largest lead of the game. The Gaels coasted to the buzzer, winning by 14 points.
Iona (9-8, 6-2) also beat Siena last Sunday 87-78, and has won seven of its past eight meetings.
Mike Brey is looking at former Notre Dame players to fill two assistant jobs that have opened up with the departures of Martin Ingelsby and Anthony Solomon.
Purdue's 2016-17 prospects got a jolt Wednesday when forward Caleb Swanigan announced he will return for his sophomore season.
Clemson's Jaron Blossomgame says he is withdrawing from the NBA draft and returning to school for a final season.