Adam McQuaid, David Krejci and Greg Campbell also scored for the Bruins (12-2-2), who won their fourth straight to bolster their best start since the 1976-77 season. All four victories have come on the road, where the Bruins are 8-1-1.
Casey Cizikas scored for the Islanders, who are a league-worst 2-8 at home.
The Bruins came out flying, punishing the Islanders along the boards at both ends of the ice and not relenting for 60 minutes. Boston is 16-3-1 in its last 20 games against the Islanders, who remain in the basement of the Atlantic Division.
The bruising defenseman McQuaid started the scoring at 6:43 of the first with his first goal of the season, a shot from the right point that squirted through the pads of Islanders goalie Evgeni Nabokov.
Center Tyler Seguin skated out of traffic in the left circle to make the pass to McQuaid. The assist was the 100th point of the 21-year-old Seguin's career. The second overall pick of the 2010 draft is on five-game points streak with a goal and four assists.
Cizikas tied the score at 15:49 of the first when he jammed a rebound past Tuukka Rask. Josh Bailey raced down the right side and swooped in front of Rask, backhanding a shot toward the goalie. Cizikas tapped in the loose puck for his second goal of the season.
That was all the Islanders could muster in their second straight loss. They had won four of six games before squandering a 2-0 lead against Carolina on Sunday and losing 4-2.
Marchand put Boston up 2-1 with his team-leading 10th goal of the season 38 seconds into the middle period when he backhanded a rebound past Nabokov. Patrice Bergeron assisted on Boston's first two goals.
Krejci made it 3-1 with a perfect one-timer from the left circle off a backhand pass from Milan Lucic at 5:16 of the second period, and Campbell scored into an empty net at 18:55 of the third for his second of the season.
Rask made several terrific saves among his 36 stops.
The Finnish goaltender twice denied Michael Grabner on breakaways and made a nifty block on Frans Nielsen while the Bruins were short-handed in the first period. He twice stopped defenseman Mark Streit with spectacular glove saves and smothered a Kyle Okposo point-blank slap shot early in the third.
The 25-year-old Rask is 6-0-1 in his last seven games, a stretch in which he has not surrendered more than two goals in regulation.
Boston's league-best penalty kill stymied the Islanders three times. The Bruins have 24 consecutive penalty kills since allowing a power-play goal in Montreal on Feb. 6. They have stopped 58 of 61 chances this season.
The Islanders, who play nine of their next 12 games at home, were playing their second on a seven-game homestand.
NOTES: The game was the 150th meeting between the teams, with the Bruins holding a 77-48-21-4 edge over the Islanders, who joined NHL in 1972 . Bruins coach Claude Julien is third in franchise history with 240 wins, trailing Milt Schmidt (245) and Art Ross (361) . The Bruins are 8-1-1 in their last 10 visits to Nassau Coliseum . Islander LW Matt Moulson's games-played streak stands at 266. The only Islanders with longer streaks are Billy Harris (576) and Bobby Nystrom (301). ... Boston beat the Islanders 4-2 in the first matchup Jan. 25 at TD Garden. The teams play again April 11 in Boston.
This program aired on February 27, 2013. The audio for this program is not available.