A jet ski's factory horn is a small electric beeper, and at speed, over engine and wind noise, other boaters barely hear it. A battery train horn gun gives you a real blast on a personal watercraft (PWC) without wiring anything into the hull. The catch: a PWC is the wettest place you can take one, so the questions are where it rides, how you keep the tool battery dry, and how you keep from losing it overboard.
Does a PWC legally need a horn?
Yes. A Jet Ski®, Sea-Doo®, or WaveRunner® is a vessel under the Navigation Rules, and every vessel under 12 meters (39.4 feet) needs "some other means of making an efficient sound signal." There's no decibel minimum and no approved-device list. State guides list a handheld air horn, a sports whistle, or an installed horn as acceptable. Your voice doesn't count.
State rules sit on top of that. Texas Parks and Wildlife lists "one sound-producing device" on its required-equipment list for PWCs, along with a wearable life jacket for every rider (no inflatables) and an engine cut-off lanyard if the craft has one. Many riders meet the legal minimum with a whistle clipped to their life jacket. The problem is that a whistle doesn't carry far over idling engines in a crowded cove, never mind a busy sandbar on a Saturday afternoon.
A horn gun clears the legal bar easily, but it doesn't replace the rules about when and how to signal. Our USCG sound-signal requirements guide walks through the regulation line by line. For signal patterns and emergency use on larger boats, see train horn guns for boats and marine signaling.
When a loud horn actually matters on a jet ski
PWC riders don't need a horn often, but when they do, they need it to be heard right away:
- Blind corners on rivers and narrow channels. A prolonged blast (4 to 6 seconds under Rule 32) warns traffic coming around a bend before anyone can see you.
- The danger signal. Five or more short, rapid blasts (Rule 34) says you don't understand another vessel's intentions or doubt it's doing enough to avoid a collision. It's the signal a PWC rider is most likely to use when a boat drifts toward a swimmer or a towed tuber.
- Group rides. One rider with a horn can call a spread-out group back together or stop it, which is hard to do by waving your arms from across the water.
- Breakdowns and fog. A PWC that won't restart is a small, low target. A horn you can sound again and again on a fresh battery is easier to hear than a whistle you're blowing with salt in your mouth.
One caution: you sit within arm's length of the trumpets on a PWC, and a passenger sits even closer behind you. Point the bells forward and away from people, and keep blasts short unless you're signaling in fog.
Which horn gun fits on a PWC
Space is the real limit. As one example, BRP lists the 2022 Sea-Doo GTI SE with about 8.8 L (2.3 gal) of glovebox and about 144 L (38 gal) of front storage, while the 2022 GTX Limited has a glovebox of only about 2.9 L (0.8 gal). In practice, a horn gun with a battery attached rides in the front bin. Even a big glovebox can't hold one.
If you already run Milwaukee® M18™ tools, the 5-Trumpet Horn Gun for Milwaukee® 18V Battery is the loudest option we build. It's rated up to 150 dB, has five metal trumpets, and comes with a remote that works up to 160 ft. It is also the largest of our guns. On a two-seater with a small bin, a dual-trumpet model packs down tighter and is still far louder than a stock PWC horn.
Whatever battery platform you already own is the right one to pick, because you carry spare packs you trust instead of buying into a new system. Dual-trumpet versions are available for most of the common tool batteries.
Keeping the tool battery dry on the water
This is the part that kills horns on PWCs. We cover it in full in Is a battery train horn gun waterproof?, but the short version is that our horn guns are water-resistant, not waterproof. They don't carry an IP rating, and they aren't meant to be submerged. Spray on the trumpets doesn't hurt anything. Water in the battery is what does the damage.
Milwaukee's own battery service bulletin explains why. Heavy rain, a flooded toolbox, or a drop in a puddle can let water into a pack through the power-terminal opening. Its advice is to remove an exposed pack right away and turn it on edge to drain. A PWC hull is a lot wetter than a flooded toolbox, and salt water conducts electricity far better than rain. Set it up like this:
- Ride with the battery out. Store the gun and the pack separately in the front bin. A pack snaps in within seconds, and the terminals stay sealed inside a dry bag until you need them.
- Use a roll-top dry bag. PWC storage bins aren't reliably watertight and can take on water on rough days. A dry bag sized for the gun is the cheapest insurance you can buy.
- Never charge on the dock. Bring packs inside to charge, away from spray and damp.
- Rinse after salt water. Wipe the trumpets and housing with a damp freshwater cloth. Don't hose the gun. Let it air-dry with the battery out, and check the pack's contacts for white or green residue before the next ride.
Tethering: don't lose it overboard
Don't count on a horn gun floating, especially with a battery attached. Assume anything you drop off a PWC is gone. Treat it like any other loose gear on a sit-on craft:
- Use a coiled lanyard from the gun to a D-ring or grab handle, not to your body. If you go in the water, you don't want a heavy horn hanging off your life jacket.
- Keep it separate from the engine cut-off lanyard. Since April 1, 2021, federal law has required operators of most recreational boats under 26 feet to use an engine cut-off switch when running on plane, and the Coast Guard notes that 44 states have their own ECOS laws for PWCs. That lanyard has one job, which is killing the engine if you fall off, so never clip anything else to it.
- Use it off plane. The only time you should have the horn in hand is idling, drifting, or stopped. At speed, both hands belong on the handlebars.
Mounting it vs. carrying it
Some riders want the horn fixed on the craft so they can fire it without opening a bin. The wireless remote makes that possible: a gun strapped near the rear grab handle with a remote on your wrist or the handlebar. It's the most exposed setup, though, because the gun and battery take every bit of spray and every wake. If you mount it, keep the battery out until you're on the water, ride in fresh water when you can, and take the whole unit off before trailering. Our ATV, UTV, and boat mounting guide covers bracket options. For most PWC owners, though, a dry bag in the front bin that you can grab in a hurry is the better tradeoff.
FAQ
Can I use a train horn gun instead of a whistle on my jet ski?
Federally, yes. Vessels under 39.4 feet just need an efficient means of making a sound signal, and a horn gun qualifies. Check your state's boating handbook for any extra rules, and keep a whistle on your life jacket as a backup that works even if you end up in the water.
Will salt water ruin the horn?
Spray on the trumpets won't. Salt water reaching the battery terminals or the electronics will, over time. Keep the battery in a dry bag until you need it, wipe the gun down with fresh water after each ride, and store packs indoors.
Is 150 dB too loud for a PWC?
Not on open water when you're signaling for safety. It is too loud to point at a passenger or a nearby swimmer. Aim the trumpets away from people, and save long blasts for fog or emergencies. Many lakes also have local noise rules, so don't use it for fun near docks.
Can I leave the horn gun on the PWC overnight?
Don't. Take it and the battery home after every ride. Dew, rain, and dock-line spray add up, and a pack that sits damp is how terminals corrode.