Wheaton lead by as many as eight (15-7) in the first half, but Coast Guard tied the game 24-24 on a three-pointer by H.B. Baker with 8:30 left.
Coast Guard took its only lead of the game 36-34 on the a three-pointer by Peter Gavin with 2:39 left in the half, but Wheaton scored the final six points of the half for a 40-36 lead at the break.
Coast Guard scored the the first basket of the second half before the Lyons used a 12-0 run capped by a Mike Stanton three-pointer to take their biggest lead 52-38 with 15 minutes left.
The Bears got as close as five at 67-62 on a three-pointer by Mark Schiavoni with 2:44 left.
James Greenslit added a career-high 15 points while Josean Vega had added 13 points for Wheaton (12-6, 3-3).
Jason Nelson had a game-high 23 points for Coast Guard while Dan Sheppard and Ryan Ball added 10 points each for the Bears (3-12, 0-6), who dropped their seventh straight.
Sheppard had a game-high 12 rebounds for Coast Guard.