St. Bonaventure, seeded 14th, led for the first 34 minutes of the game but stalled and Florida State took advantage with a 12-0 run for the lead. The Seminoles' first lead of the day came at 55-52 with 5:19 to go on an Ian Miller 3-pointer.
The Bonnies (20-12) had a last charge, with Andrew Nicholson's 3-pointer cutting the Florida State lead to three points. Clutch 3-pointers from Demitrius Conger kept St. Bonaventure tight but the Bonnies missed a couple of shots in the final seconds, which gave Florida State the chance to escape.
Loucks scored six of his 13 points in the final 3 1/2 minutes, including three late free throws.
The Seminoles (25-9) will next face Cincinnati in the tournament's third round Sunday in Nashville. The No. 6-seeded Bearcats (25-10) eliminated Texas 65-59 in Friday's first game.
Bernard James, hitting 8-of-11 shots from the floor led Florida State with 19 points and nine rebounds.
Nicholson led all scorers with 20 points while Conger had 14 points and nine rebounds and Conger finished with 14 points.