He made his debut over the distance at the Edinburgh Marathon in 2006, finishing in fourth place with a time of 2:17:38.[1] Under the tutelage of former world record holder Paul Tergat, Chelimo significantly improved upon this the following year. He ran a personal best of 2:11:56 for second place at the Belgrade Marathon, finishing three seconds behind John Maluni, and he felt it was clear he needed more training to improve further.[2] He knocked two minutes off his best with of run of 2:09:42 at the JoongAng Seoul Marathon, although this was only enough for fifth place in a quick race won by Joshua Chelanga.[3]
His first marathon of 2008 came at the Twente Marathon, where he was out of the medals with a fifth-place finish.[4] He returned to Seoul for another attempt at the JoongAng Marathon race and the competition developed into a duel between Chelimo and Solomon Molla. He set a best time of 2:08:51 but it was his Ethiopian rival who took the honours, five second ahead.[5] He began his 2009 season at the Daegu Marathon, where he ran 2:10:13 for sixth place.[6] He took part in the Great Scottish Run in Glasgow that September and recorded a time of 1:02:25 for fourth place in the half marathon event.[7] The typically fast Amsterdam Marathon saw Chelimo pitted against top competition. His run of 2:07:46 was another improvement over the distance, but he finished fifth as fellow Kenyans Gilbert Yegon and Elijah Keitany took the top two spots on their event debuts.[8] His third marathon performance of the year came in December at the Honolulu Marathon and he was second behind defending champion Patrick Ivuti.[9]
At the Nagano Marathon he controlled the race, gradually pulling away from the rest of the field to record his first victory over the distance.[10] He came within a fraction of a second win of 2010 at the Eindhoven Marathon: a sprint finish between Chelimo, Charles Kamathi and Paul Biwott left him as runner-up to Kamathi. The winning margin was so narrow that Chelimo's new personal best time of 2:07:38 was the same as that recorded by the winner.[11] He won the Honolulu Marathon in December with a time of 2:15:18 hours. The following year he came sixth at the Vienna City Marathon,[12] but he returned to the top of the marathon podium at the Honolulu race, taking a second consecutive victory.[13]
Chelimo had two marathon outings in 2012, but both were poor ones as he was seventeenth at the Eindhoven Marathon and eighth in Honolulu, failing to break two and a quarter hours on both occasions. The 2013 Los Angeles Marathon saw him return to form with a third-place finish with a time of 2:10:44 hours and the Cologne Marathon saw him return to the top of the podium with his first sub-2:10 marathon in three years (2:09:45).[14]
