Harry Sinden, general manager of the Boston Brunis, and Tom Johnson his assistant flew from Montreal to Boston today, after first convincing customs agents that they had, indeed, spent only one day in Canada, despite all that luggage.

Like so many others connected with the Stanley Cup playoffs the Bruins' brass had expected to pass the rest of the week in Montreal. But the New York Islanders increased airline business and emptied hotels by defeating the Canadiens, 4-3, in overtime Tuesday night, forcing a sixth game in the best-of-seven series here on Thursday.

With their unused clothing, Sinden and Johnson carried word back to Boston coach Don Cherry from Al Arbour, his opposite number with the Islanders.

"Tell Grapes we wish him well and he may be seeing us in that final, after all," Arbour said.

"Grapes" is the not-so-sour appelaltion for the guy who is busy accepting congratulations for the Bruins' four-game sweep of the Philadelphia Flyers, an accomplishment that has Montrealers and others wondering whether the Canadiens' "dynasty" will survive a second season.

Along with Arbour's message, johnson planned to relay some comments of his own, like "Bob Gainey's breakaway looks alot bigger now. Going back to Long Island, those fans could help win another one for the Islanders and in a seventh game, well, anything can happen."

After Montreal had taken a 3-2 lead in the third period Tuesday, Gainey broke free and put a bodacious deke on Islander goalie Chico Resch.It seemed like the clincher but Resch, starting his first game of the playoffs, dove to his left and somehow blocked Gainey's backhander. Moments later, Jude Drouin's shot hit Montreal defenseman Guy lapointe in the chest and caromed into the Canadiens' net to tie it.

Then it was Billy Harris providing the winner at 3:58 of overtime and suddently the airlines, phones were very busy. Perhaps a lot of the people who confidently made those week-long reservations in Montreal had something to do with the surprising finish, only the second loss on home ice for the Canadiens in their last 53 games.

"People kept talking about the Canadiens' next series, but this one isn't over yet," said winger Bob Nystrom. "We're been coming back all year.

"All we've been reading and hearing is how Montreal is ready for Boston," Arbour said. "Maybe now the momentum is going to change in favor of us. At least it should be a big boost for us."

Montreal golie Ken Dryden figures that the Canadiens, despite coach Scotty Bowman's warnings, might have been thinking too much about Boston, too.

"It could be that we were wishing an end to the series instead of going out and creating an ending," Dryden said.

Certainly, if the sixth game constitutes an inconvenience for reporters and league officials, it represents a much more annoying situation for the Canadiens. Even should they end the semifinal Thursday night, it means 60 or more minutes of pounding from the close-checking Islanders, and that will not help when the well-rested Bruins finally make it to Montreal.

Pierre Bouchard, who suffered a slight shoulder separation three weeks ago, is expected to rejoin the Canadiens for Thursday's game. His absence was notable Tuesday, when Rick Chartraw's holding penalty led to an Islander power-play goal and Chartraw's score by Dave Lewis that was disallowed, as being pushed in, by referee Bob Myers.

Thursday's game will be shown on Telscreen at Capital Centre along with four new Hartland Monahan commericals (cartoons?) at 8 p.m. Admission is $3, with no charge for parking. Capital officals were among those hoping a Boston-Montreal final would be starting Thursday, to capitalize on the large number of Bruin fans in the area. Now they're hoping those fans will be interested in alook at the final-series opposition. Whoever that may be.