Hella Marine Supertone Twin Horn Kit 118 dB 12V

The Hella Marine Supertone horn kit gives you two horns that work as a team. One puts out a 500 Hz high tone, the other a 300 Hz low tone, and when they sound together you get a full, layered blast that reads as 118 decibels. That's the kind of signal that actually cuts through wind, engine noise, and a busy channel, which is exactly what you want when you're closing on another boat and need to be heard right now.

Each horn measures 4.7 inches round and runs on a standard 12 volt system, pulling about 5.5 amps (roughly 72 watts) when both are sounding. The housing is steel with a black finish and a red protective grille over the diaphragm. It's a simple, honest piece of gear. No app, no fuss. You press the button, it's loud.

Who's this for? Center consoles, walkarounds, sailboats, pontoons, small cruisers, really any 12 volt boat that needs a proper sound signal. The U.S. Coast Guard requires vessels under 20 meters to carry an efficient sound-producing device, and at 118 dB this kit clears that bar with room to spare. It's also a common upgrade on boats where the original single horn has gone quiet or tinny with age.

Why two tones instead of one? A single-frequency horn can get lost against wind and water noise, especially at a distance. Stacking a 300 Hz low tone under a 500 Hz high tone gives the sound more body and makes it carry farther across open water. It's the same idea behind the classic dual-trumpet sound, and it's why boaters keep coming back to the Supertone setup year after year.

A word on wiring, because it matters here. At 5.5 amps, you don't want to run this straight off a dash button. Wire it through a relay and let the horn button trigger the relay coil. That keeps the heavy current off your switch and stops the button from overheating over time. Protect the circuit with a 10 amp fuse and run 14 AWG wire. On longer runs past about 15 feet, step up the wire gauge to keep voltage drop from robbing you of volume.

Mounting is straightforward, but two things are worth knowing. First, mount the two horns a bit apart, somewhere in the 12 to 18 inch range, so the two tones don't fight each other and cancel out. Second, angle each horn 10 to 15 degrees downward, or add a small drain hole, so rainwater and spray drain out instead of pooling on the diaphragm. Do that and you'll get a lot more life out of them.

Be honest with yourself about the environment. This is a steel-bodied horn with a plastic grille. In hard salt-air service it wants a little care. Rinse it with fresh water when you rinse the rest of the boat, keep the terminals coated with dielectric grease, and mount it somewhere with at least some shelter from constant spray if you can. Treated well, it's a reliable, great-sounding horn. Left to soak in salt and neglected, any steel horn will complain eventually.

Installation is usually well under an hour if you already have a switch and a spot picked out. Most owners run a fused hot from the battery to the relay, tie the horn button to the relay trigger, and ground both horns to a clean, paint-free point on the hull or a bonded ground bus. Give the connections a good crimp, add heat shrink over the terminals, and you've got a setup that'll answer every single time you hit the button. The kit includes both the high-tone and low-tone horns. A relay isn't part of this particular kit, so if you don't already have one in your horn circuit, grab one along with the fuse and wire.