The crash was reported to the state police about 9:30 p.m. Saturday.
Cpl. John MacDonald of the Maine Warden Service says the people in the boat included people staying at a local camp. The boat operator worked for the camp.
WGME-TV reports three of the four injured people were taken to Rumford Hospital, while the fourth, who suffered a slight laceration, drove himself.
Two of the more seriously injured people were flown to a Lewiston hospital while the third was taken there by ambulance. The fourth injured person drove himself to the hospital.
All are expected to survive.
The incident remains under investigation.