CSkipR - being in NSB, your block heaters really shouldn't be necessary at all. Even if, during the winter, the ambient air temp drops into the 20's (as you know, not often), the water temp under your boat is still in the 40-50º range. I have found it more than sufficient to run the engines up to operating temp and then shutting down. This gets the ER pretty cozy, usually in the 70º range. I've even gone as far asopening the salon hatches afterward and allowing the cabin heat/AC to help keep the interior warm. Just a thought.
BTW, how are those coaming pads working out?