Here's the best way IMHO to prevent runaway boats due to switch failures.
The "old school" Noble switch is made for vibration and is double throw, triple pole, so it's like having 3 switches in one. Available from Pete Waters at Kraft Midwest, 248-486-4800. I use a spring from an OS carb on the Dubro pushrod to spring load it "on" and jam a piece of wood against it to hold it off, this way I can cover it with a waterproof boot.
Another way is to put the spring on the other side of the rod and hold it off with a clothespin.
Pete also told me if you unplug your battery pack between outings they'll be alot less of that green stuff around.