Art Welch, who admits he doesn't even know all of his teammates' names yet, earned the title of hero yesterday when he hammered in a goal with 55 seconds left in the second overtime to lift the Washington Diplomats over the Seattle Sounders, 3-2, in a North American Soccer League game at RFK stadium.

A crowd of 17,736, the second-largest home attendance in Washington's history (35,620 witnessed the Cosmos-Dips game in 1975), watched the home team rally from a 2-0 first-half deficit, English striker Bobby Stokes, who scored the winning goal in the Dips' 2-1 win over Chicago last week, scored two unassisted goals to set up the overtime.

Washington, with an overwhelming 35-12 shot advantage, almost pulled out the game in the first 7 1/2-minute extra session as Welch, Mike Lester and Jimmy Redfern barely missed scoring.

With time running out in the second overtime and the fans preparing themselves for the tie breaker "shootout," Welch gathered in a pass from Stokes just outside the Seattle penalty box.

Welch, a 33-year old Jamiacan who is the ninth-leading scorer in NASL history, cranked up and booted the ball between surprised Sounder defenders and just outside the reach of goalie Tony Chursky.

"I don't think they expected me to shoot from out there," said Welch, who entered the game for midfielder Gary Darrell with 23:36 remaining in regulation. "But at that stage of the game when you get close, you take the shots. I think the goalie's vision was slightly blocked and he never saw it coming.'

Washington coach Dennis Viollet, who played two years with his newly acquired forward when both were with the Baltimore Bays in the late "60's, knew exactly what Welch could do.

"Art is fast, sharp and knows the game," said Viollet. "Both teams were a bit tired and I wanted to give Art and Tony (Macken) a half-game. I wasn't particularly anxious about going into the shootout. I would have just asked fo volunteers. If no one volunteered, well then . . ." The shootout occurs if the teams are tied after the completion of two overtimes. Each team gets five chances, beginning from the 35-yard line, to beat the goalie in a one-on-one contest within a five-second span.

For most of the first half and the opening minutes of the second, the Dips did everything possible to score. Darrell, Redfern, Lester and sStokes could only shake their heads time and time again as their 10-foot attempts sailed awry. On one occasion late in the first half, the Dips, with seven players within spitting distance of the goal, took five shots and missed them all.

"We kept creating chances. I felt we would win if we got that first one," said Viollet.

Washington came on strong again after intermission. Macken, who replaced an ineffective Mark Liveric, and Alan Spavin continued to push the ball upfield against an eight-man Sounder defense and hope for the smallest crack.

On a Washington corner kick, Seattle's Dave Gillet made a fine play as he headed the ball outside the penalty area. But Stokes controlled the carom and rolled a hard shot under Chursky's dive from 20 yards out.

Stokes tied the game at the 70:10 mark, scoring on another 20-footer after a Seattle defender cleared a lob pass out of the Sounder area.

The Sounders seemed to falter in the heat and were content to sit back and play defense. Washington's back line of Ken Hill, Roy Willner, Don McAllister and Jim Steele merely began helping out at the offensive end.

"We were exhausted. That game was played at a fast pace," said McAllister.

Before most of the fans had firmly settled in their seats, Seattle's Mickey Cave took a pass from Harry Redknapp and beat Washington goalie Eric Martin to put the visitors ahead, 1-0, with just 53 seconds gone.

While Washington was going through the "just-missing-and-almosting" blues, Seattle jumped ahead, 2-0. Dip defender Hill was called for a hand ball in the penalty area and Seattle was awarded a direct free kick. From 12 yards out, Paul Crossley easily blasted the ball past Martin.

'I guess we're used to that now,' said Martin referring to the goal scored by Fort Lauderdale just 23 seconds into the game two weeks ago. "Then they go two up. You are expected to win at home but it's tough when you're behind by two goals at half. Not many teams can come back from that."

The victory evened Washington's season mark at 3-3. It earned nine points for a total of 26 but the Dips still are nestled in the cellar in the powerful Eastern Division.

Washington Plays its next three games on the road in a nine-day span.