Well, Nancy caught me with her electric blanket, so I had to go to plan 2 for winterizing the boat. I know there is a lot of criticism for putting any kind of heat source in the motor compartment, but in my life around light bulbs, I've never had one explode or otherwise cause a spark. So I took my heavy duty drop cord and 100 watt bulb, protected by a wire cage and placed it between the two sets of CMI's. Just for fun, I also hung a thermometer from the hatch pin. After a really cold snap at Lake Mead, +/- 30 low to +/- 50 hi, I sneaked up on the boat, threw off the cover, unsnapped the cockpit cover and raised the hatch. It was 55 degrees in there!
One final note. Voltage runs high in Boulder City, usually around 128V (close to the dam you know) so we buy mostly 130V bulbs rather than 120V bulbs. The filaments are heavier and I have yet to blow any bulbs in the house or garage. Just thot this may help someone. However, if you blow up your boat, don't call me...