Patrice Bergeron, Matt Bartkowski and Brad Marchand scored for the Bruins. Niklas Svedberg started in goal, stopped seven of eight shots, and was replaced halfway through the game by Jeremy Smith, who made 15 saves.
Islanders defenseman Scott Mayfield scored an empty-net goal at 18:49 of the third period.
The teams play again on Friday in Bridgeport, Conn.
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