Goals from Neil Gauld, Paul Lawson, Derek Young and Conor Gethins secured an impressive victory for Formartine over Keith.
Ryan Keir’s wonderful free-kick on the stroke of the break capped a great performance from a player who didn’t deserve to end up on the losing side.
The home side dominated early on and broke away with Michael Ewen cutting inside from the right to cross the ball into Craig MacAskill, whose powerful strike was well saved by keeper Andy Reid.
Kris Duncan then attempted to chip Reid from inside the penalty area, but the ball went over the crossbar.
At the other end Scott Barbour sent in a dangerous cross from the left however there were no takers in the box.
Keith hit United on the counter again with Keir driving into the box, but he decided to try and set-up one of his team-mates instead of shooting.
Keir then curled in a shot from 18 yards out which struck off a post.
In the 40th minute Formartine opened the scoring with their first shot on target through Gauld, who half-volleyed the ball into the net after a defensive mistake.
Keith levelled the scoring just before the break as Keir stepped up to curl a set-piece from the edge of the box beautifully into the top left corner of the net.
Formartine retook the lead in the 50th minute when Young smashed the ball into the net. The former Aberdeen player then fell down in pain and was replaced by Neil McVitie.
Things got worse for Maroons boss Allan Hale’s side as United were awarded a penalty by referee Liam Duncan after Gauld was adjudged to have been taken down inside the box. Lawson stepped up to calmly slot home the spot-kick.
Soon after Formartine manager Kris Hunter decided to put on Gethins to take the place of Gauld. Former Nairn player Gethins grabbed his first goal in a United shirt at the death as he tapped in from close range.