SEATTLE, AUG. 13 -- The telephone lines carried only good news back to the Vulcan Foundry in Denham Springs, La., tonight. Of course, Ben McDonald backers have come to expect nothing else.

While McDonald's parents gathered by a phone at his mother's workplace in his home town for inning-by-inning updates from the Kingdome, the Baltimore Orioles' precocious rookie pitcher secured another record with another night of superlatives. He limited the Seattle Mariners to four hits and two runs in 8 2/3 breathtaking innings, and the Orioles benefited for a 3-2 win here before 21,253.

McDonald won for the fifth time in five major league starts. His ERA rose to a still-nifty 1.55 and he broke Jerry Walker's club mark set in 1957-59 by capturing his sixth career decision without a loss. He escaped a tense moment during a comparatively shaky first inning, but was touched only for Edgar Martinez's fifth-inning double that led to Seattle's only run, plus two singles by Alvin Davis and one by Omar Vizquel.

"He had good control and command of his pitches," Orioles Manager Frank Robinson said. "It's not that he's getting better, it's that he's starting to feel more comfortable out there and starting to settle and do some of the things he's capable of doing.

"When he has his good stuff, he doesn't care who's out there. It was not what Seattle didn't do, it's what Ben McDonald did."

McDonald retired 12 of the final 14 batters he faced, ending with three strikeouts and three walks. He has allowed 41 hits and 15 earned runs in 53 2/3 big league innings, 26 hits and seven earned runs in 36 2/3 innings as a starter.

"I was confident about myself, but I didn't expect to do this," McDonald said.

Gregg Olson allowed Martinez's RBI single in the ninth but got the final out on Scott Bradley's liner to second, stranding runners at first and third and earning his 27th save.

Mariners starter Brian Holman was solid in extending Seattle starters' remarkable steak of pitching at least into the seventh inning in 31 of the last 33 games. He allowed only six hits while pitching a complete game.

But Holman (11-8) picked the wrong night on which to take the mound, for McDonald (5-0) made Cal Ripken's RBI double in the first and a two-run fourth stand.

The Orioles improved to 56-58, including 3-4 on their nine-day western road trip. They're six games behind Boston in the American League East.

The Mariners, who lost for the sixth time in seven games, fell to 58-58, fourth in the AL West. In 12 games this month, Seattle has scored 32 runs.

McDonald seems to gain a bit more command on the mound and raise his confidence another notch with each outing. And his stature in the Orioles' clubhouse has grown with each victory -- to the point that he has become almost as revered by his teammates as by the opponents who nonchalantly sidle by to view his warm-up tosses in the bullpen before a game, then think nothing of comparing him to Roger Clemens.

"You get the feeling like you're in on the ground floor of something big," Orioles catcher Bob Melvin said. "It's exciting to be around."

"He's a gifted, special kid," Seattle Manager Jim Lefebvre said. "Forget 'gonna be'; he's a helluva pitcher already."

McDonald's numbers pale in comparison with Fernando Venezuela's rookie run in 1981 -- winning his first eight starts, with seven complete games and a 0.50 ERA -- but no one associated with the Orioles is complaining. "He has shown he can be a real outstanding pitcher in this league, something special," pitching coach Al Jackson said. "Now it's just a matter of him getting the work he needs to reach his peak."

McDonald was sharp from the beginning tonight, though he had to struggle through a first inning in which he pitched out of a two-out, two-on jam after walking Ken Griffey Jr. and allowing a single to Davis.

He retired Pete O'Brien on a liner to center to end that threat, and he breezed through the early going from there. His fastball was overpowering the Mariners, and his curve was somewhat wild early on but just effective enough to keep them off balance.

The Orioles gave McDonald a 1-0 lead in the first off Holman, who had won his last three decisions. Brady Anderson walked with two outs, then scored on Ripken's sharp double to the right-center field alley. The RBI was Ripken's 15th in 11 games and his 10th hit in his last 24 at-bats with runners in scoring position.

He has hit safely in 14 of 16 games, becoming one of the few mainstays in a sagging Orioles attack that had mustered but 13 runs in five games before Sunday's 11-run outburst against Mark Langston and the California Angels.

Baltimore extended the advantage to 3-0 in the fourth. Ripken led off with a solid single to center, and went to third on a bloop single to left by Joe Orsulak one out later. Chris Hoiles scored Ripken with a bouncer to third baseman Martinez that forced Orsulak at second but was too slow for the Mariners to turn a double play.

Holman then committed a costly error, balking the lead-footed Hoiles to second. Craig Worthington, who has hit safely in eight straight games but still entered tonight hitting .191 over the past two months, followed with a run-scoring single to center.

Meanwhile, McDonald was in command. His curve came around as the game progressed, and he retired 10 of 11 batters between Davis's single in the first and Martinez's leadoff double in the fifth. He faced Griffey, the AL's third-leading hitter beginning the day, with two outs and Vizquel at second base in the third. Griffey flied weakly to center.

But Seattle did turn Martinez's double into a run. Bradley advanced him to third with a grounder to second baseman Rene Gonzales, and Vizquel scored him with a sacrifice fly to narrow the deficit to 3-1.

Orioles Notes:

Third-base coach Cal Ripken Sr. returned to Aberdeen, Md., after the death of his mother late Sunday. Claire Oliver Ripken was 93.

Ripken will rejoin the team Friday in Baltimore. Shortstop Cal Ripken Jr. remained here. Second baseman Bill Ripken is on the disabled list and not traveling with the team.

First-base coach Johnny Oates moved to third tonight, and batting coach Tom McCraw took over at first. . . .

Pitcher Bob Milacki threw for 12 minutes off a mound today. He said the effort gave him no reason to doubt his strained right shoulder will be healed sufficiently when he's eligible to return from the disabled list in eight days. . . .

Hoiles, who was promoted from Class AAA Rochester late Sunday, started at first base, where Robinson said he will get a lot of playing time. Hoiles was zero for three, scored a run and had one RBI.