Graham Mertz threw for 259 yards, Trey Smack kicked five field goals and the defense of No. 25 Florida limited visiting Charlotte in a 22-7 win Saturday night in Gainesville.Coming off an upset of then-No. 11 Tennessee, the Gators (3-1) started fast, scoring on their first four possessions as Mertz completed his first seven passes. But the rest of the night was a struggle for Florida.Charlotte (1-3) stayed close as it repeatedly stopped the Gators when backed into its own territory, forcing Florida to settle for field goals.The Gators’ defense ultimately paved the way, limiting the 49ers to 210 yards and 10 first downs.Mertz completed 20 of 23 passes with a touchdown. Ricky Pearsall had six receptions for 104 yards, including a sensational one-handed grab in the first half that set up one of Smack’s field goals.Running behind a Florida offensive line that was missing three injured starters, Montell Johnson Jr. grinded for 63 yards on 16 carries and Trevor Etienne added 48 yards on eight rushes.Florida opened the game with a remarkably efficient, nine-play, 95-yard march in which it didn’t face a third down. Mertz went 3-for-3 in the drive for 51 yards with the last 6 coming on a touchdown pass to Arlis Boardingham.The Gators increased their lead to 16-0 as Smack followed with field goals of 27, 23 and 54 yards.