Marmolejos' first big league homer was a three-run shot in the first inning. J.P. Crawford led off the game with a single, Kyle Seager drew a two-out walk and Marmolejos, a rookie first baseman, sent a fastball from Dylan Bundy (1-1) into the elevated stands in right field.
"I wanted to be aggressive with the runner in scoring position," said Marmolejos, who came into the game with only two hits in his first 18 at-bats. "I was looking a little more middle and away, but I wanted to get a swing there."
Long Jr. had two hits. The Mariners led 3-2 when he opened a five-run ninth by hitting Hansel Robles' fastball over the wall in right. Crawford and Kyle Lewis each had two-run singles in the frame.
Shohei Ohtani hit a three-run homer off Dan Altavilla in the Angels' ninth. Ohtani's 42nd home run in the majors tied him with Kosuke Fukudome for fifth-most by a Japanese-born player.
Gonzales (1-1) provided a lift for a Mariners' pitching staff that had allowed seven runs or more in their first six games. The left-hander allowed only two unearned runs in 6 1/3 innings on six hits with six strikeouts and a walk.
His only mistake came in the fifth inning, when he hung a curveball that Matt Stassi hit off the right-field foul pole for a two-run homer.
"I was confident he would go deep into the game," Seattle manager Scott Servais said. "He was laser focused on attacking the strike zone and got ahead in a lot of the counts."
Gonzales also continued his mastery of the the Angels in their home ballpark. He is 4-0 with a 2.63 ERA in seven starts at Angel Stadium.
The Mariners dropped four of their first five to start the season but have won two straight.
Brian Goodwin added two hits for Los Angeles, which has lost four of its last five after splitting its first two games. The Angels have allowed 18 runs the past two games, with 13 being surrendered by the bullpen.
"We played relatively well enough to be in good position record wise. You really can't anywhere without a substantial bullpen," manager Joe Maddon said.
TROUT OUT OF LINEUP
Angels star outfielder Mike Trout was placed on the paternity list before the game. The reigning AL Most Valuable Player and his wife, Jessica, are expecting their first child.
Maddon said after the game he didn't know if the baby was born yet. "The manager is always the last to know," he said.
Bundy settled down after Marmolejos' homer and allowed only two hits the rest of his night. He retired nine straight at one point.
"It wasn't actually a bad one. You hit your spot and the guy guessed right," said Bundy of the home run he allowed. "He was able to get to the heater and put three runs on the board pretty quickly and it was a battle from there."
The right-hander -- who was acquired from Baltimore during the offseason -- went six innings and allowed three runs on four hits with eight strikeouts. He is the first Angels' pitcher since Jered Weaver in 2012 to go at least six innings and have seven or more strikeouts in his first two season starts.
Lewis extended his hitting streak to seven games to begin the season and has five straight multihit contests. He is batting .448 this year, including 11 for 22 with five RBI in the last five games.
Mariners: C Austin Nola (knee soreness) went through some pregame workouts and could return to the lineup on Friday.
Angels: SS Andrelton Simmons said he feels as if his sprained left ankle isn't as bad as last year's injury, which kept him out for five weeks. Simmons is on the injured list after he rolled the ankle off the back of the first-base bag during Monday's game at Oakland when he was trying to beat out a groundball.
Mariners: Begin a 10-game homestand with Friday's night home opener against Oakland. Taijuan Walker (0-1, 13,50) makes his second start of the year.
Angels: Open a three-game series against Houston on Friday. Right-hander Matt Andriese (0-0), who tossed 5 2/3 innings of shutout ball in relief at Oakland last Sunday, gets the start.
More AP MLB: https://apnews.com/MLB and https://twitter.com/AP-Sports
Ohtani plants a 99 mph heater out of the yard
Shohei Ohtani drives a fastball to deep left-center field for a three-run home run.