The player-coach touched down twice in the first half and again after the break to ease his side’s relegation fears and encourage hopes that a play-off spot may yet be within their grasp.
March said: “We executed well, we played for 80 minutes and that’s all I’ve been asking for all year.”
Seven first-half tries saw Keighley lead 34-0 at the break.
Ritchie Barnett opened the scoring in the fourth minute and then Josh Lynam added a second six minutes later.
Keighley continued to probe and scored again through Barnett in the 14th minute to cap a breathless opening.
The Cougars began to run amok with Danny Lawton scoring twice to put the result beyond doubt.
It was soon time for March to claim centre stage, with the player-boss crossing the line twice in quick succession before the break to make it 34-0.
Whitehaven replied after the break through Joe Greenwood but March soon completed his treble and Lynam’s second, coupled with Joe Chandler’s late effort, meant scores from Lee Doran and former Bulls half-back Cain Southernwood were immaterial.
Whitehaven: Thorman, Calvert, Cameron, McAvoy, Fleming, Rooney, Southernwood, Houghton, Newton, Jackson, Doran, Clarke, Clough. Substitutes: Sice, Patterson, Greenwood, Cullnean.
Keighley: Moss, Barnett, Williams, Lawton, Duffy, Jones, March, Shickell, Feather, Sheriffe, Chandler, Lynam, Rawlins. Substitutes: Hesketh, Law, Bailey, Kelly.