The former World champion needed the win on the scenic Kerry course to carry his hopes of a 13th Irish championship title to the final race on the Galtees in two weeks time.
The Kerryman’s main rival, Scottish international and former Ben Nevis race winner John Brooks, missed the race due to a niggling injury leaving the pair with two wins and a second each in the five race Arup series.
The Irish title will now hinge on the result over the tough Tipperary course.
Lenihan took advantage of the Scot’s absence to impose himself on all his rivals for the Irish team for the World championships at Sauze d’Oulx in Italy.
He relentlessly pulled out an insurmountable margin on one of his favourite courses.
Lenihan had over a minute in hand after a tight battle between Sean O’hEigeartaigh, George Lonergan, Alan O’Shea, and Gerry Brady as they reached the Devil’s Punchbowl below the summit.
At the summit, Lenihan had held his advantage while Lonergan and O’hEigeartaigh were inseparable in joint second with O’Shea and Brady just behind.
Beth McCluskey took the women’s race from Orla Touhy with Alwynne Shannon third.
Micheal Lyons and Rose Twohig won the junior men’s and women’s races respectively.