Russell (Boo) Bowers' two free throws with four seconds to play assured American University of a 78-77 victory today over Lafayette College in the Eagles' season opener in the East Coast Conference.

AU, winner of three straight on the road after loses to Rutgers and Maryland, never led in the second half until Bowers hit a 10-footer with 3:30 to play to make the score 72-71. Bowers, averaging 27.4 points, finished with a game-high 33.

Lafayette, which won the ECC West Division a year ago and earned a berth in the National Invitation Tournament, led at half, 38-36, and moved out to a 69-60 lead with seven minutes to play behind the scoring of guard Mike Whitman and forward Tom Best. Best had 27 points, Whitman 21. g

But AU outscored the Leopards, 12-2, to take the lead. Ed Sloane and Dennis Ross made free throws and Sloane followed a missed free throw by Ross to narrow the gap to 69-64.

Bowers made two shots and, after a Lafayette free throw, Sloane's basket pulled AU to 71-70. A bad pass by the Leopards' Charles Keller gave the ball to AU and Bowers put his team ahead.

Gordon Austin, who finished with a career high 17 points, made two free throws for AU after Lafayette players had missed three straight. Best's basket cut AU's lead to 74-73 and the Eagles held the ball until center Juan Jones was fouled with 21 seconds remaining. He made both free throws.

Whitman made two foul shots for Lafayette with six seconds to play. Bowers then took a full-court pass from Mark Nickens, was fouled by Best and made the free throws. Whitman scored at the buzzer.