Hoey carded three birdies, five bogeys and a double bogey to lie nine under, seven behind leader Alvaro Quiros.
Spaniard Quiros fired a 70 as he aims for his seventh European Tour victory.
Zander Lombard is second on 11 under, followed by Pep Angles - who shot the lowest round of the day with a 68 - and Renato Paratore, both on 10 under.
Hoey, along with English duo Lee Slattery and David Horsey, will be part of a group of six players who will start nine under in Sunday's final round at Verdura in Sicily.
The players struggled in the wind, with an average score of 74.1 compared to the opening round's 68.9 and 69.3 on the second day.
Hoey recorded two birdies and two bogeys on his outward nine, but then dropped shots at the 10th, 16th and 17th and took a double bogey at the 13th and made his sole birdie coming home at the 12th.
Sweden's Sebastian Soderberg went into round three level with Hoey in second place but a 77 saw him fall back to seven under.
Former Masters champion Mike Weir is level thanks to a third-round 76, having made his first halfway cut since November 2014 on Friday.
Weir, who has slumped to 1,907th in the rankings, has struggled for form since undergoing elbow surgery in 2011 and announced in July 2015 that he was taking an indefinite leave of absence from golf for family reasons.
Northern Ireland's Michael Hoey posted a disappointing four-over-par 75 in the third round of the Rocco Forte Open to drop down to a tie for fifth position.