We have not found any need for a bullhorn on the boat so we don't carry one.* However we know people who do and it works for them.
When we bought it our boat was equipped with a panel-mounted loud hailer/intercom and when the original unit burned up (literally, one more reason we never operate the boat from the flying bridge) we replaced it with a Standard Horizon LH5. It comes in extremely handy, particularly when anchoring. There is a two-way horn mounted to the overhang over the windshield and a two-way speaker up on the flying bridge.
The horn above the windshield provides a great way for the person running the boat and the person operating the anchor windlass to communicate. We tried the walkie-talkie headsets and found they were more of a hassle than a benefit so we got rid of them. With the loud hailer/intercom we just talk to each other.
The intercom is also very useful when guests want to ride up on the flying bridge. We can carry on a conversation with them from the lower helm station, which is the only helm we use.
The LH5 incorporates a variety of timed horn signals. While the speaker horn is not anywhere near as loud as the boat's dual air horns, the loud hailer horn provides a nice timer for blowing the air horns. When the loud hailer horn goes off whoever's at the helm hits the button for the air horns.
When running in the fog it's sometimes impossible to hear the horns of vessels around us over the engines under the floor. By switching the intercom function to the speaker horn we can amplify the outside sounds so we can hear them inside at the helm station over the noise of the engines. This is particularly helpful when we are cruising in the fog through the channels and passes used by the Washington State or BC ferries.
The one thing we have not used our loud-hailer for is communicating with another boat or people on shore. But I've been on a friend's LCM6 landing craft when he used the same Standard Horizon LH5 setup we have to communicate with our wives on a pier during a tricky docking in very high winds, and it worked very well.
We don't use our loud-hailer/intercom a lot but it has proven to be the best communication solution for those situations it's suited for.
There are fancier and more versatile hailer/intercoms on the market--- Furuno makes a pretty snazzy one, the LH3000, that has a very snazzy price tag to go with it--- and some of the upper end VHF radios incorporate hailer/intercom functions, too, if you don't want to install and wire up a stand-alone hailer unit.
We've found the Standard Horizon LH5 is just fine for our needs, and since it was replacing the earlier hailer there was already a place in the panel for it and the wiring, two-way horn and flying bridge speaker were already installed.* But if you're installing electronics and wiring from scratch you might find one of the high-end VHF units with a hailer/intercom function to be a more compact way to go.
-- Edited by Marin on Sunday 28th of November 2010 03:35:01 AM