Larsen and McDonald each made five shots from the field while Lasan Kromah, who had led George Washington (3-3) in scoring the past two games, finished with 10 points on 4-of-6 shooting.
The game went back-and-forth, as neither team led by more than four. Charles Cooke broke the games' seventh tie with a free throw to put James Madison (1-5) up 48-47 with 3:12 left.
But the Dukes would not see the lead again, as Larsen hit a layup to help George Washington retake the lead, 52-48, and Patricio Garino hit a 3-pointer to put the Colonials ahead for good.
James Madison scored just one basket over the final two minutes before Andre Nation sank a desperation heave at the buzzer.
A cameraman fell down trying to film Ben Simmons at the NBA Draft. Flashing back to his LSU days proves this is nothing new.
ESPN's Dan Dakich joins The Paul Finebaum Show to discuss the SEC's presence in the NBA Draft.
Ted Kapita was the top-rated recruit from West Virginia in the class of 2015 and recently played at DME Academy in Florida.