Montana’s Boating Under the Influence (BUI) Laws

Read about the consequences of boating under the influence (BUI) in Montana.

Montana law prohibits operating a motorboat while under the influence of drugs or alcohol. The term “motorboat” means “a vessel, including a personal watercraft or pontoon, propelled by any machinery, motor, or engine of any description, whether or not the machinery, motor, or engine is the principal source of propulsion.” (Mont. Code Ann. §§ 23-2-502(7)(a), 23-2-523(2), 23-2-525(5) (2016).)

For purposes of Montana’s BUI statute, “under the influence” means that “as a result of taking into the body alcohol, drugs, or any combination of alcohol and drugs, a person’s ability to safely operate a vehicle has been diminished.” (Mont. Code Ann. § 61-8-401(3) (2016).)

BAC Levels and Presumptions

Montana law includes "presumptions" about a person's impairment based on blood alcohol concentration (BAC). The presumptions apply to the determination of whether the boater was under the influence.

Presumption boater was not under the influence. If a boater’s BAC was .04% or less, the judge or jury can presume the boater wasn’t under the influence. So, for example, a jury could presume a boater who had a BAC of .03% was not under the influence. But the prosecutor would still have the opportunity to convince the jury otherwise—“rebut the presumption”—with evidence of impairment, such as slurred speech and poor field sobriety test (FST) performance. If the jurors are unimpressed with the prosecutor's evidence, they can stick with the presumption that the defendant was not under the influence.

Presumption boater was under the influence. With a BAC of .08% or more, the judge or jury can presume the boater was under the influence. To rebut the presumption, the defense might present evidence of things like safe boat navigation prior to the stop or good FST performance. 

No presumption. BACs between 04% and .08% can be considered by the judge or jury, but no presumptions apply.

(Mont. Code Ann. § 61-8-401(4) (2016).)

BUI Penalties

Montana BUI penalties depend on the circumstances of the case. But generally, a BUI is a misdemeanor. Convicted boaters typically face $15 to $500 in fines and/or up to six months in jail. (Mont. Code Ann. § 23-2-507(1) (2016).)


Sentencing law is complex. For example, a statute might list a “minimum” jail sentence that’s longer than the actual amount of time (if any) a defendant will have to spend behind bars. All kinds of factors can affect actual punishment, including credits for good in-custody behavior and jail-alternative work programs.

If you face criminal charges, consult an experienced criminal defense lawyer. An attorney with command of the rules in your jurisdiction will be able to explain the law as it applies to your situation.

Talk to an Attorney

If you’ve been arrested for or charged with boating under the influence in Montana, get in contact with an experienced BUI attorney. The facts of every case are different. A good BUI attorney should be able to explain how the law applies to the facts of your case and help you decide on your best course of action.

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