I have had the same problem. Since your boat has a tarp, consider using the attached driveway alarm. If someone gets in your boat, it will notify you. This depends upon where you place it. Normally when I am traveling on the road for King Kat tournaments, I use it. I have to watch were I place it. If I have it to high, it will pick up cars passing. I want to detect their feet. Less false alarms. I also get a room that I can see my boat. Check Harbor Freight out. Search results for: 'alarm'