My 47 Eastbay has them, so no, it doesn't have to be a 100' option. They're spendy and you don't really 'need' horns all that often, but when you do it's nice to have LOUD ONES.
A scuba regulator 1st stage that is a diaphragm design works perfectly as they are usually adjustable between 20 and 160 PSI. Mine happens to be an Oceanic, but any should work. You will need to add an overpressure pop off valve and an adapter from 3/8" straight thread oring seal to 1/4" FPT or MPT. If you head down this path, I can point you toward the adapters if you can't find them.
Between the tank, 1st stage regulator, some fittings and a pressure gauge, your probably looking at $500 new. I had everything used lying around, rebuilt everything, and had next to nothing in the setup. CO2 would certainly be a cheaper initial and continuing cost. See warning about CO2 at the end of the post.
CO2 is a liquid that vaporizes in the tank as it's used, just like propane. Filling the same tank to around 2,000 psi with air, the tank with CO2 will have approximately 3 times as much gas at ambient pressure as the air tank.
I like my scuba tank system although it is more costly for initial purchase. The big risk with CO2 is that if you develop a leak, depending where the leak is, it could easily kill you! My tank is in my pilothouse. With the pilothouse windows and doors closed, if the tank emptied, approximately 50 cuft. of CO2 would be in the pilothouse, enough to easily kill me. With the tank in the engine room, if it leaked down over a few days, there might be enough to kill you when you went down to do the prestart engine room check.
Food for thought when dealing with CO2.
Ted
No, not at all. CO2 in air is about 400 PPM (Parts Per Million) (0.04%). OSHA safe limit is 30,000 PPM (3%) for limited exposure. CO2 is fatal to humans after 30 minutes at 10,000 PPM (10%). As the percentage rises, time till incapacitation and then death drops dramatically.
Stopping distance? Bigger boats take longer to stop/change course. A horn with longer range could give notice sooner. A horn like that on a smaller boat might give the wrong impression as to the emerging situation? That'd be my guess.
I never want to assume how much or little someone else wants to spend. I go with advising what I've known to work.
