I have one of the exact same units. Two days ago it saved my boat from some serious damage.
There was a 50'+ trawler
anchored nearby with a party on board in Boca Raton. When they pulled anchor
they went into reverse and came right at us. A quick blast from that horn brought him to a stop, at which point the captain
came rushing out the back to see what was up. He had stopped about 10 metres from us. He then proceeded in forward, away from us and left.
Without that horn I am sure he would have run right into us before even realizing he was in reverse.