After falling behind 5-0 to start the game, Clark then scored 22 of the next 30 points for a 22-13 lead with 9:05 left in the first half.
The Cougars pushed their lead to as many as 17 at 40-23 and led 46-33 at halftime.
Coast Guard (3-11, 0-5) battled back in the second half as the Bears outscored the Cougars 17-4 to start the half and tied the game 50-50 on a three-pointer by Peter Gavin with 11:41 left in the game.
Clark (10-6, 5-1) responded with six straight for a 56-50 lead with 9:17 to go.
With Clark leading 67-61, Coast Guard used a 10-2 run as the Bears took their first lead of the second half, 71-69 on a basket by Dan Sheppard with 2:21 left.
The Bears had tied the game 69-69 on a three-pointer by Ryan Ball with 3:10 to play.
Clark tied the game 71-71 on a basket by James Collins and took the lead 73-71 on a bucket by Mark Stukowski with 1:04 left.
Tim Dutille made the first of two free throws for Clark with 13.9 seconds left, giving the Bears a chance to tie.
Dave McNamara led four Clark players in double figures with 16 points while Brent Kenneway and Dutille each had 15 and James Collins had 10 points. Dutille led the Cougars with 12 rebounds for his first double-double of the season.
Mark Schiavoni had a game-high 20 points for Coast Guard while Kevin Edes and Dan Sheppard each added 14 points to go with Jason Nelson’s 12 points. Sheppard had a game-high 12 rebounds for Coast Guard.