Security Alarm for $10
This is a “pull pin” personal alarm. When the pin is pulled, a 90 dB alarm sounds. It’s loud. I have found these at Lowe’s and Home Depot for about $6.
As you can see, there is a key ring attached to the main part, and a small ring with a cord on it attached to the pull pin. One idea is to tie the key ring to something on one side of your cockpit floor, then tie a mono-filament line to the pull pin, and run the line across the floor to the other side of your cockpit. When the intruder walks onto your boat, he trips the pin, and the alarm sounds.
I used to work at Camp Hugo in the Florida Keys. We had both girls and boys at the camp. I did something like this in front of the girls dorm. I tied two empty coke cans together across the steps. I ran the mono-filament line between the cans. They wouldn’t see the line, and the cans would make plenty of noise as they got dragged round attached to someones ankle.
At one time I had one of these personal alarms rigged on my companionway hatch. If someone cut off the lock, and slid the hatch back, the alarm would go off. I had about 3-4 inches of slack in the pull cord line so that I could reach in and unhook the pin cord before sliding the hatch back. You would have to know this trick in order to disarm it.
I suggested this to a friend in my marina. He hooked it up as I described above, and it worked for him one night. Some guy try to break into his boat, but set off this alarm, and took off. The person in the slip across from his heard the alarm too, and called my friend.
Think of the places you could rig these. The dinghy, the generator, the kayak, or, just carry it to town in sketchy places as a personal alarm. That’s how they are originally intended to be used.
It could also be used as an alarm on a man overboard line that is towed behind the boat.