The Scotland international scored twice in two minutes early in the second half of Saturday's Scottish Premiership clash to turn the game in the hosts' favour, just when the sides were locked at 1-1.
Before Boyd's brac,e Dale Carrick had equalised for Hearts after his team-mate, Danny Wilson, had handed Kilmarnock the lead with an own-goal.
The trend of goals coming in pairs continued as Michael Gardyne scored just three minutes after Sam Nicholson's strike to give the hosts' hopes of avoiding the relegation play-off spot a welcome boost.
Kilmarnock opened the scoring after 25 minutes when Rory McKenzie drove down the right wing and lashed a cross into the area, where the retreating Hearts captain Wilson could only divert the ball past Jamie MacDonald for an unfortunate own goal.
The visitors were not behind for long however, as the lively Carrick chased down a speculative high ball over the top and with Craig Samson and Lee Ashcroft hesitating, the young frontman nipped in to lift the ball over Samson into the unguarded goal for just his second goal of the season.
The home side moved ahead just four minutes into the second half, Boyd out-muscling Jamie Hamill to get on the end of a loose ball and put a low left-foot effort past MacDonald for his 17th goal of the season.
The prolific striker had to wait just two more minutes for goal number 18, the Scotland forward finishing high into the roof of the net at the second attempt after an initial effort had been blocked.
Hearts breathed new life into the contest after 67 minutes when substitute Billy King ran down the right before picking out Nicholson in the area, who perfectly timed his arrival to slot past Samson.
Gardyne, though, tapped home at the near-post to restore Kilmarnock's two-goal cushion after 71 minutes.
Hearts substitute Paul McCallum had a late header disallowed for offside, but there was to be no further scoring as Killie gave themselves some vital breathing space at the foot of the table.