So here's the "egg on my face" part - as it turns out, both batteries were "fried"; that is, not capable of retaining a charge. One big lesson learned has been that "Maintainance Free" on a battery label does not mean MAINTAINANCE FREE. In my case both batteries had removable caps on the cells, and I should have been monitoring electrolyte levels and topping off as needed. Here in the Central valley of Calif we have summers with temps exceeding 100 deg. for extended periods. Batteries, particularly flooded, lead-acid type, don' t like this condition, and discharge at a much higher rate. In addition, these batteries had been manufactured in 2008 and then installed in our 2009 boat at the factory. All of these factors contributed to their ultimate demise.
Initially, the house batt was holding some level of charge, and I was lulled into a false sense of security that I could continue to use the jumper cables to allow engine starts. Wrong! So while tied up between two great restaurants in Newport Beach, we met the nicest guy who responded to our Vessel Assist call with a portable starting unit.
So now Kamalani is sporting two new AGM Glass-Mat, truly Maintainance-Free batteries. These are hopefully more forgiving of the hot climate, and presumimg I can keep a proper charging routine going during storage periods, they will outlast the prior flooded ones.