Review on 🚢 2-Pack 12v 150dB Truck Train Horns - Ultra Loud Snail Air Horns Kit with Relay Harness for Vehicles - High-Volume Electric Train Horn for Trucks, Cars, Motorcycles, Boats, and Ships - Horn with Wire (Red) by Rob Marsh

Decent set of horns for the money. Probably not as many decibels as they advertise, but definitely someone will know you're there. A simple mounting bracket makes the installation more flexible and high quality. The installation instructions are small and difficult to read, but use a different instruction for the horn. I was finally able to get it to work. Installed on the boat. The blue wire goes to the horn. The white wire is GND (in my configuration) which keeps me guessing it's not the black wire. This includes black earth going to the horn compressor. And YES, I am NOT an electrician.