"I've only seen one other guy, Mark McGwire, hit a ball that far, especially in this ballpark," Marlins manager Mike Redmond said. "He's got some sick pop."
Stanton turned on a Dallas Keuchel changeup for his second three-run homer in as many days and fourth home run of spring training. Stanton also lined a single in the fourth, raising his batting average to .333 and his slugging percentage to .692.
"You can tell he's starting to swing the bat well," Redmond said. "You can tell he feels good. That's fun to watch, that's for sure."
Casey McGehee hit a three-run double into the right-center field gap in the second and was thrown out trying to stretch it into a triple.
Keuchel, who hadn't allowed a run in nine innings during his three previous spring training starts, gave up seven runs and 13 hits in four innings.
"They had a better plan than I did in the first two innings, and I just didn't make an adjustment," said Keuchel, a candidate for a rotation spot.
Marlins starter Jacob Turner allowed one run, two hits and three walks in five innings.
"After the first inning I felt good," Turner said. "I made a lot of good, quality pitches, got my changeup working, which I was happy about."
Jake Marisnick, Reed Johnson and Derek Dietrich all had three hits for Miami.
Houston: Keuchel went 6-10 with a 5.15 ERA last season, but Astros manager Bo Porter attributed those numbers to a handful of poor outings.
"If you look at his whole body of work, he put together a pretty good season last year," Porter said.
Miami: Jacob Turner looks stronger than last year and has impressed the Marlins with his velocity.
"I think he's throwing the ball harder," Redmond said. "I know velocity-wise we've seen some mid-90s fastballs this year, which we didn't see last year."
Marlins second baseman Rafael Furcal (hamstring) took batting practice and went through some baseball activities on Tuesday. He could return to major league action in a few days. Ed Lucas also is dealing with a hamstring issue and could appear in a minor league game on Thursday.
TIMING IS EVERYTHING
Marcel Ozuna is struggling with his timing at the plate, which explains his .135 average. Despite the sluggish start, Redmond said the Marlins aren't expecting to have their projected opening day centerfielder begin the season in the minors.
"I still expect him to be out there on opening day," Redmond said.
Pitcher Mark Appel, the first pick in the 2013 amateur draft, could be close to making his spring training debut following an appendectomy.
"He's getting close," Porter said. "It's one of those things that we didn't want to rush him."
Redmond announced Tom Koehler will start a minor league game on Wednesday a off day for the Marlins major leaguers. Brad Hand also is slated to pitch an inning of relief in that game. Koehler and Hand are competing to become Miami's fifth starter. Jose Fernandez is to start Thursday against St. Louis, followed by Nathan Eovaldi at Houston on Friday. Kevin Slowey and Henderson Alvarez will start split-squad games Saturday.