"I felt good," Willis said. "I've been feeling real strong the last three starts. I haven't been getting the results I want to of late, but we got some early runs, we played defense and I felt confident out there."
Willis (6-3) stopped a personal two-game losing streak. He gave up five hits, three walks and struck out seven. The left-hander had two complete games -- a rain-shortened five-inning win in 2003 and an eight-inning loss last year -- in his only other two starts against Tampa Bay.
"He goes out there and keeps us in the ballgame," Florida manager Fredi Gonzalez said. "Sometimes when the other team gets to him, he still keeps us in the ballgame and that's what you ask for from a starting pitcher."
Hermida hit a two-run homer off Jae Seo (2-4) to give the Marlins a 5-1 lead. Boone, who hit a grand slam in Florida's 8-4 win on Friday, then connected for his third homer of the season on the next pitch.
"That's always nice ... when you're scoring runs, hitting the ball out of the ballpark," Boone said. "That makes it fun for everyone."
The Marlins have won four of five following a four-game losing streak.
"It's not about results, it's just about the effort level," Willis said. "You go out there and leave it on the field. That's all you can ask from a ballclub, especially a young ballclub. So that's all I was asking for and we responded, and hopefully we continue all the way to the end of the season."
Seo, who had his ERA climb from 7.26 to 7.80, will remain in the rotation.
"He just got some pitches in some bad spots," Tampa Bay manager Joe Maddon said. "I really don't have answers for you. We'll continue to work with him. When it comes time to make certain moves, when that occurs, we'll all get together. But for right now, that's not what is going to happen."
Seo said he had some problems with his slider and that the Marlins were "aggressive" at the plate.
Miguel Cabrera had an RBI single and Hermida hit a sacrifice fly to put the Marlins ahead 2-0 in the first. Hermida has a hit in six straight games since returning from a right knee injury.
Dukes led off the bottom of the first by smashing a home run an estimated 428 feet to center. It was his second leadoff homer this season.
Hanley Ramirez extended the Florida lead to 3-1 with a solo homer in third.
Gomes hit his first homer since last July 29 in the seventh.
Tampa Bay catcher Josh Paul underwent postgame X-rays on his left arm. He hurt the arm on a play at the plate in the sixth.
Paul's arm was hit by the leg of a sliding Miguel Oliva when he tried to reach across the foul line to apply a tag. Paul stayed in the game.
"It hyperextended a little bit," Paul said. "I was good to go. They're just making sure. It was a weird play, that's all.
The Marlins placed RHP Ricky Nolasco (right elbow inflammation) on the 15-day disabled list and purchased the contract of RHP Justin Miller from Triple-A Albuquerque. ... Dukes has eight homers this season. All have been solo shots. ... Willis has given up a homer in eight of his 10 starts. ... Seo has just three wins in 25 starts for Tampa Bay since being acquired from Los Angeles last June.