ll season long, the New York Islanders heard the knocks. Like the refrain of some top 40 tune, the accusations followed every loss. Those Islanders, they're spoiled by their three Stanley Cups. They're just bored, and they'll never be able to turn themselves around in the playoffs.

"Everybody said it all year," said Denis Potvin.

So much for popular opinion.

With a decisive 8-3 victory over the Boston Bruins here Tuesday night, the Islanders played one of their strongest playoff games, took a 3-1 lead in this semifinal series and proved they are moving into high gear in time for what is now anticipated as a dynamic final round against Edmonton and Wayne Gretsky.

"We won't look ahead to that," said Clark Gillies, raising an eyebrow. "They've got a young bunch of guys, and I do enjoy beating them every time we do it. That would be a helluva series. I'd enjoy seeing that myself."

Maybe none of the Islanders want to look that far ahead, with at least Thursday night's game remaining against the team that was the regular-season league leader in points. But, after two consecutive lethargic performances by the Bruins, the temptation is hard to resist.

"In the playoffs, everything means more," said Potvin. "Yeah, we are playing better, and we do have guys who come on stronger then. It's funny to say, but the fact that you can see an end coming, that each game is one game closer to putting another team away."

Potvin predicted that his club's confidence will be high Thursday night, because of the chance for a series victory.

"I think the game last night (Tuesday) was a critical one, maybe the most important we played all year," he said. "This is when we come on."

Boston hopes to delay that finality at least one more game. The Bruins had played poorly last Saturday, and although the Islanders did not play up to their playoff standard, they beat Boston, 7-3. Boston goaltender Pete Peeters had a tough time that night, but his second appearance at Nassau Coliseum was even worse, particularly during the third period when the Islanders beat him for five goals in just under six minutes.

None of the Bruins offered any substantial explanations for their collapse. "I just don't know what happened to us," said Mike Krushelnyski, who scored Boston's first two goals. "Maybe we got tired. And now we have to go home and defy the odds."

Defenseman Brad Park looked as weary as the rest of his teammates. "We made mistakes and the Islanders took advantage," he said. "We have to find a way to counter them now if we hope to get back into this thing."

Peeters didn't offer any excuses for his play. At one point in the third period, just after Mike Bossy had beaten him for a hat trick, it appeared Boston Coach Gerry Cheevers might relieve his goaltender with the score 6-2.

Cheevers called a timeout and summoned Peeters to the bench, but sent him back into the game with a pat on the back. "Gerry just told me to hang in there," Peeters said. "He knows I'm not going to quit on anybody. The Islanders taught us a good lesson. I hope we learn something from it."

Should Boston win Thursday, a sixth game would be played here on Saturday, and if necessary, a seventh would be in Boston Garden Tuesday. If the Islanders win Thursday night, they will begin the finals in Edmonton on Sunday night.