Vanek had an assist in Friday's victory. He now has three points (one goal, two assists) in as many games since being traded to New York by the Buffalo Sabres this past Sunday.
"I think we worked hard again," said Vanek, whose goal was his 500th NHL point. "That's two nights in a row we've put 60 minutes together and deserved to win."
"I don't know what you want to call it, but I call it not good enough," Bruins coach Claude Julien said of his team's performance. "There's no way in the world you should come in here and play the way you play. We're not competing hard enough. We're just not good enough right now. You see the difference in the team that beat you tonight. The energy and the effort that was put in compared to us … sometimes you think you're working hard, but you're not, so we've got to certainly rectify that and try and get our team back on track. Talent alone is not going to win you hockey games."
Tavares broke a scoreless tie at 6:15 of the second period. With the teams at even strength, Vanek took the puck off David Krejci's stick in the slot and quickly put a shot on goal that was denied by Johnson. But Tavares was on the doorstep and showed some nifty hand-eye coordination and swatted the puck out of midair and over the goal line for his sixth goal of the season.
MacDonald doubled New York's lead with his first goal of the season at 13:13. MacDonald, who had three goals in 48 games last season, took a pass from Travis Hamonic and one-timed a slap shot from the left point that found its way through a crowd and past Johnson to give the Islanders a 2-0 lead.
"We didn't give them a whole lot," Tavares said. "We seemed to take it to them and control the pace of the game and when we're able to do that, I like our chances. I thought [Friday] was a pretty good game too. Obviously we gave up a couple more goals [against Ottawa], but obviously 5-on-5, I thought we played the 200-foot game really well."
The Bruins responded quickly via the power play on a goal by Hamilton at 15:27. With three seconds remaining on a holding-the-stick penalty to Islanders forward Brock Nelson, Hamilton sent a cross-ice feed from the right circle toward Carl Soderberg, but New York center Frans Nielsen accidentally poked it through Poulin's pads to make it 2-1. Hamilton was credited with his third goal of the season.
Vanek restored New York's two-goal lead 41 seconds later with his first goal as an Islander. He finished off a 2-on-1 with Kyle Okposo (two assists) by one-timing a feed from the left circle past Johnson to make it 3-1. It was Vanek's fifth goal of the season and 30th in 51 games against the Bruins.
Johnson denied Vanek's bid for his second of the night midway through the third period. Vanek made a nifty move around Hamilton and snapped a wrister that Johnson snared with his glove to keep it a 3-1 game.
"I think those guys, they're highly skilled, they're different players, but you can see now playing together for a couple of games, the chemistry's starting to click there," Islanders coach Jack Capuano said of his top line of Vanek, Tavares and Okposo. "I was pleased with their work ethic. I don't know the final minutes, I know they played close to 23 minutes [Friday] night. They played a lot of minutes tonight. I thought they did a lot of good things not only offensively, but they did some good things as well without the puck."
Poulin, who made his third start of the season, responded nicely from his previous appearance, a 5-2 loss against the Philadelphia Flyers last Saturday. The 23-year-old stopped all 12 shots he faced in the third period to help New York preserve its lead.
"Overall, I think my game was good tonight," said Poulin, who earned his first win of the season. "Win or lose, sometimes you just have to focus on what you do, and what I did tonight was good. I don't think I made a lot of mistakes, but it wasn't perfect."
The Islanders begin a four-game road trip Tuesday against the Washington Capitals. Boston plays the first of a five-game homestand Tuesday against the Dallas Stars.