A.J. English scored 16 points and had nine assists, six rebounds, three steals and three blocked shots for the Gaels.
Williams' 3-pointer with 14:27 until intermission gave the Gaels a 12-11 lead they would never relinquish. Williams hit another 3 24 seconds later, and in less than five minutes Iona raced to a 29-13 lead with 9:42 before the break.
Iona recorded nine 3 pointers in the first half and led Marist 52-26 at halftime.