After a start delayed by 45 minutes because of a wet outfield, England’s bowlers came out firing.
They were given a helping hand by a combination of a mix-up between the West Indies openers and brilliance in the field from Jacob Bethell to run out Shai Hope.
Mahmood removed Evin Lewis in the next over before setting up Roston Chase superbly to have him caught at first slip in the fourth.
Jofra Archer bowled Pooran in between and when Mahmood had Hetmyer caught in the deep, West Indies were reeling.
For Mahmood, who exploited friendly bowling conditions brilliantly, it is now a record-breaking eight wickets in the powerplay in this series – the most by any bowler in a bilateral T20 contest.
Powell led the recovery with a well-paced half-century as he and Romario Shepherd steered West Indies away from immediate danger – both showing the Daren Sammy Cricket Ground was too small for them when they connected cleanly.
The Windies skipper reached his seventh T20 international fifty from 36 balls but just when he and Shepherd would have hoped to accelerated, the latter fell lbw after he was deceived by a superbly disguised Overton slower ball.
Overton removed Gudakesh Motie in the same over and then came back to have Powell caught in the deep to start his next.
There looked like being an element of symmetry to the innings before a late flurry from Alzarri Joseph and Akeal Hosein ensured the hosts batted their overs to post a respectable total.