Mont. Code § 23-2-505
The owner of a vessel is liable for any injury or damage occasioned by the negligent operation of the vessel, whether the negligence consists of a violation of the provisions of the statutes of this state or neglecting to observe ordinary care and operation that the rules of the common law require. However, the owner is not liable unless the vessel is being used with the owner's express or implied consent. It must be presumed that the vessel is being operated with the knowledge and consent of the owner if, at the time of the injury or damage, it is under the control of the owner's spouse, father, mother, brother, sister, son, daughter, or other immediate member of the owner's family. This section may not be construed to relieve any other person from any liability that the person would otherwise have. However, this section may not be construed to authorize or permit any recovery in excess of injury or damage actually incurred.
§ 23-2-505, MCA