Every started the final round four strokes behind Australian Scott, but charged to the front with four birdies in a sizzling five-hole stretch around the turn at Bay Hill in Orlando.
The 30-year-old Every shot a 70 to finish at 13-under-par 275, while fellow American Keegan Bradley missed a long birdie attempt at the last that would have forced a playoff. Bradley (72) finished second on 12 under, with Scott (76) a shot further behind.
Seven clear at halfway and seemingly heading for the 11th PGA Tour title which would seem him reach world No 1 in time for the defence of his US Masters title, Scott had struggled to a third round of 71 on Saturday. That saw his lead cut to three shots and it had been wiped out by the time the Australian reached the turn in the final round, Every joining Scott on 13-under-par.
Scott had bogeyed the first after twice finding sand, while it was a hooked drive into the water on the third which cost him another bogey. The 33-year-old steadied the ship with a chip to four feet to set up a birdie on the par-5 fourth, but then bogeyed the seventh after his tee shot plugged in a greenside bunker.
In contrast, Every was two under for his round after birdies at the fourth and ninth and a bogey at the eighth took him out in 35, the 30-year-old then adding another birdie on the 10th.
Scott had held the outright lead since the early stages of his opening round on Thursday – he equalled the course record with a stunning 62 – but that was no longer the case when Every made it three birdies in four holes on the 12th.
Every holed from six feet to improve to 14 under par, one ahead of Scott and two clear of Kokrak. Every made it four birdies in five holes from 12ft on the 13th to double his lead and soon found himself three clear of the pack when Scott bogeyed the 14th. Scott’s tee shot came up well short of the green but he elected to putt through the fringe, running his birdie attempt seven feet past the hole and missing the return.
A massive swing looked to be on the cards on the 16th when Every pushed his tee shot into the trees and failed to find the fairway with his escape shot, eventually making a bogey six.
In the group behind, Scott found the green in two with a towering iron shot as Every looked on, only to then three-putt for par to remain two behind.
Every then found a greenside bunker on the 17th but saved par after his recovery shot slammed into the pin and somehow stayed out.
Meanwhile, the World Golf Hall of Fame is changing its induction process to be more equitable to male and female players.
Until now, the eligibility process for LPGA players has been more stringent, based on a points system that has kept out multiple major champions such as Laura Davies and Dottie Pepper.
Russell Knox finished joint-43rd after a closing 74 for a level-par aggregate while Martin Laird, the winner in 2011, ended up last of the 76 players to qualify for the final 36 holes. He finished on nine-over after a last-round 78.
Meanwhile, several male players without any major titles, including Colin Montgomerie and Masashi “Jumbo” Ozaki of Japan, have been inducted.
Male and female players will now need at least 15 wins on a recognised tour, or two major championships, to be eligible.
Among other big changes, selection will be governed by a 16-person committee, co-chaired by former playing greats Arnold Palmer, Gary Player, Nancy Lopez and Annika Sorenstam.
Each nominee needs to receive 75 per cent of the committee’s vote to gain induction.