Chris Johnston and Rory McKenzie were also on target for lowly Kilmarnock who made it six successive wins at Tynecastle in this one-sided encounter.
The visitors needed just 13 minutes to open the scoring after dominating the early stages.
Ever-green Boyd headed home at the far post, as he found the bottom right-hand corner of the net from Johnston's cross.
Two minutes later he almost added a second only to be denied by home keeper Jamie MacDonald.
MacDonald was also called into action on 19, saving McKenzie's low shot.
The visitors doubled their advantage six minutes before the break thanks to Johnston's 25-yard curler which flew into the top right-hand corner of the net.
And the three points were all but secured four minutes into the second half when Boyd slotted home his second of the afternoon from 12 yards, latching on to McKenzie's measured assist.
Boyd wasted a chance to claim his hat-trick on 52 and, shortly afterwards, lifted another opportunity over the bar.
Callum Paterson threatened on occasions for the hosts, while Brad McKay headed high and wide following a free-kick but, by then, Hearts were already three goals behind.
With 90 minutes on the clock, McKenzie completed the scoring with a well-struck effort from 25 yards after collecting Johnston's pass.