Big lake safety equipment
Getting about that time of year...don't forget to re-check all your safety gear for your boat.
Saw this on another board. This along with some tapered wood dowels should help keep you floating if you loose a thru-hull.
http://www.stayafloatmarine.com/usa/ This stuff seems like a tapered, solid plug of toilet bowl wax ring material. I am sure that would work as well and it's probably a lot cheaper. Won't take up much room and could save your vessel someday.