Mike Boddicker earned a called strike on his first pitch to each of Seattle's three batters in the first inning tonight. It was a sign of things to come.

Boddicker, the Baltimore Orioles' leader in walks, permitted only one as he pitched a six-hit shutout, struck out nine and breezed to a 7-0 victory over the Mariners.

The Orioles' batting heroes were Larry Sheets, who drove in four runs, and Mike Young, who had two RBI to boost his August total to 32, a club record for one month.

Boddicker's performance was a welcome one for the Orioles, since he had struggled to a 5-12 record in his previous 19 starts after a 42-20 mark from April 1983 to May 1985.

"This was the first time all year I could consistently hit corners with my fast ball," said Boddicker (12-13). "I was out ahead of a lot of hitters. When you're hitting the corners with your first pitch, they'll usually take it.

"A lot of it was just confidence, the way you feel that you're going to go out there and beat somebody. I felt I was going to win."

Seattle has been a patsy for Boddicker, managing only two earned runs in 33 career innings, so he had some reason to expect success. Additionally, he had beaten Oakland with a complete-game effort in his previous start.

"The last few games have been pretty good," Boddicker said. "The difference is strikes."

Boddicker, who did not allow more than one base runner in any inning tonight, has walked 79 in 180 innings, far above past ratios.

Young, batting left-handed against starter Billy Swift, produced the only run the Orioles needed in the fourth inning, when he lined a homer over the Baltimore bullpen in left. It was his 22nd, half of them coming in his last 22 games.

When Young walked with the bases full in the fifth, the RBI enabled him to surpass the club record for one month of 31, shared by Boog Powell (July 1969) and Doug DeCinces (July 1978).

"A record's a record, no matter how you get it," said Young, who has 65 RBI for the season. "It's nice to be up there with the big boys. I watched Boog Powell a lot when the Orioles came to Oakland, and I've certainly seen Doug DeCinces play. But I'm glad it's over, too. You do think about things like that."

The walk to Young followed an interesting decision by Seattle Manager Chuck Cottier. With two out, an infield single by Lee Lacy and a walk to Cal Ripken were followed by a first-pitch wild pitch to Eddie Murray. Cottier then ordered Murray walked intentionally, and Swift, a 1984 Olympian who apparently had sharper recall of Young's homer than Cottier did, walked Young on five pitches.

That brought up Sheets, a frequent bench warmer since Earl Weaver's return as manager, and he lined a two-run single to right.

In the seventh, with runners on second and third and one out following singles by Ripken and Murray, Cottier signaled reliever Roy Thomas to give Young an intentional walk. This time, Sheets hit a two-run double off the right field fence. Young then scored on Floyd Rayford's single.

"I was going through a bad stretch, but I've been hitting the ball fairly hard," said Sheets, who also singled in the second for a three-hit night. "It just seems like somebody is usually standing there waiting for it.

"Tonight I rolled one up the middle and it got through. You have to have those. This was like the beginning of the season, when things were going good. I haven't produced since Earl's been here like I did when Joe (Altobelli) was here. I wish I knew the reason."

The Orioles, opening a 10-game homestand, were picking up where they left off before heading west Aug. 20. This was their seventh straight win at Memorial Stadium, all against sub-.500 teams.

The crowd of 18,915 had only one occasion to show displeasure. There were plenty of boos for Alan Wiggins in the sixth inning when Wiggins, who went zero for five, did not run out a grounder to third.

Loafing cost Seattle a run in the fifth. Al Cowens sent a long drive to deep center, and John Shelby, replacing injured Fred Lynn, backhanded the ball a couple of steps from the fence, then dropped it. Cowens, anticipating an out, trotted from first to second and was limited to a double when he easily could have had a triple.

Jim Presley, the next batter, bounced one off Boddicker's glove and Cowens reached third, instead of scoring, as second baseman Wiggins threw Presley out. Cowens stayed there as Boddicker struck out Dave Henderson and Donnie Scott.