PORTLAND, Maine — A Massachusetts boater accused of causing a fatal collision on a Maine lake has been convicted of aggravated operating under the influence. But a jury was deadlocked Wednesday on charges of manslaughter and reckless conduct with a dangerous weapon.

Prosecutors say Robert LaPointe of Medway, Mass., was drunk and recklessly speeding across Long Lake on the night when his 32-foot speedboat collided with a smaller boat. The defense contended LaPointe was not impaired and didn’t see the 14-foot boat because it was black and had its lights off.

Killed in the collision on Aug. 11, 2007, were Terry Raye Trott of Harrison and Suzanne Groetzinger of Berwick. LaPointe and his passenger survived being thrown from their boat, which sped across the lake and came to rest 100 feet in the woods.