BOSTON -- Trailing the leaders by 200 yards when the Boston Marathon slogged through Heartbreak Hill, Wesley Korir passed them one by one until he took the lead on his way out of Kenmore Square.

That's when leg cramps forced him to slow down and relinquish the lead.

"It's hot out there, in case you didn't know," he told reporters after enduring temperatures in the mid-80s to win the 116th Boston Marathon on Monday. "I knew it was going to be hot, and one important thing that I had to take care of today ... was really hydrate as much as possible. I guess my biology degree kicked in a little bit."

Singing religious songs as he trudged along the scorching pavement, the native Kenyan -- a permanent resident of the United States -- retook the lead from Levy Matebo in the final mile to cross the finish line in 84.8-degree temperatures with a time of 2 hours, 12 minutes, 40 seconds.

It was 73 degrees when the elite men took off at 10 a.m. in the Boston Marathon, and the temperature climbed into the 80s later in the day. Darren McCollester/Getty Images

It was almost 10 minutes behind the world best established here a year ago by Geoffrey Mutai and the second slowest Boston victory since 1985. Mutai, who was hoping a repeat victory would earn him a spot on the Kenyan Olympic team, dropped out after 18 miles with stomach cramps.

Instead, it was Korir who may have won a ticket to the London Games.

"To me, I think running the Boston Marathon is an Olympic event," he said. "I don't care what comes up after this, but I'm really, really happy to win Boston."

Sharon Cherop won the women's race to complete the Kenyan sweep, outkicking Jemima Jelagat Sumgong to win by 2 seconds in 2:31:50. The women's winner was decided by a sprint down Boylston Street for the fifth consecutive race -- all of them decided by 3 seconds or less.

Cherop, who was also hoping to be selected for the Kenyan Olympic team, was third at the world championships and third in Boston last year.

"This time around, I was really prepared," she said. "Last time the race went so fast and I didn't know I was about to finish. I didn't know the course well and I didn't know the finish line was coming."

Matebo finished 26 seconds behind Korir, and Bernard Kipyego was third as Kenyans swept the podium in both genders. Jason Hartmann, of Boulder, Colo., was in fourth place and the top American.

"The pace wasn't blasting, so it wasn't anything that was over my head," Hartmann said. "There were so many times that you wanted to throw in the towel, but you just fought on. I don't think that anyone coming to this race really could say they were prepared for this heat."