The Washington Capitals came here with a perfect 3-0 record today and ebullient Coach Danny Belisle joked about taking a walk across the Monongahela River. It is fortunate he did not make the attempt, because he probably would have drowned.

The Capitals' unbeaten status, appropriately, was buried in a morgue. With fewer than 500 people watching in 16,000-seat Civic Arena and the scoreboard inoperative, the Capitals dropped a 7-4 decision to the Pittsburgh Penguins.

The biggest cheer of the night was a puzzlement to the players. It accompanied the radio report of Phil Garner's two-run homer for the Pirates a mile away in Three Rivers Stadium.

Twice Washington battled tack from two-goal deficits to tie, but the Penguins finally went ahead to stay with 3:35 remaining when Pat Hughes blasted a 50-foot shot over the right shoulder of goalie Jim Bedard.

It was the third long-range score against Bedard, who hardly enhanced either his chances of playing in Washington or his trade value to Pittsburgh which had expressed interest.

Fifteen seconds after Hughes made it 5-4, Gary McAdam beat Bedard on a breakaway. Then Mario Faubert utilized an empty net to produce a 170-foot goal, concluding the scoring.

Power-play goals by Robert Picard and Mike Gartner wiped out an early 2-0 Pittsburgh lead. Then Tim Coulis and Bengt-Ake Gustafsson connected 31 seconds apart in the final period to erase a 4-2 Penguin advantage.

The game was marred by 31 penalties and it dragged out near the finish as delayed calls were required on each team. At the time of Faubert's goal, the Penguins had four players in the box serving minor penalties.

Gustafsson was shaken up in the second period when he was nailed by Pittsburgh's Rick Kehoe and Picard was winded when Faubert decked him with a solid check late in the game. In the process, Picard reopened a cut on the bridge of his nose that had been stitched up Tuesday in Springfield.

Washington played without right win Tony Cassolato, who suffered a rib-cage injury Tuesday; defenseman Paul MacKinnon, who has a sprained wrist; forwards Ryan Walter and Tom Rowe, who were given a night off, and forwards Bob Sirois and Bob Girard and defensemen Rick Green and Pete Scamurra, all nursing minor injuries at camp in Hershey.

The Capitals' rookies defeated the New York Islanders' rookies, 4-3, tonight at Long Beach, N.Y., as Steve Clippingdale scored twice.

Washington continues the current trip Thursday night in Winnipeg for its first meeting with Tom McVie's Jets.