The outside of my box is insulated as best as I can get at it combining a variety of materials from foam panels to stuffing fiberglass insulation to using the canned expanding foam. After reading all the feedback here, it seems the best implementations also include lining the inside of the box with some kind of high r value foam boards. I will most likely follow that approach. I would also like to cover that foam board with some kind of fiberglass/gel coat so that it can be easily cleaned but not sure how to make that stick to the foam boards - some research is in store there. I am also not thrilled with the ice box cover in terms of snug fit. I have added new seals all around but it still does not seem optimal. The more I look into it, the end result of dollars needed for a complete solution keeps creeping up...
* new condenser/evaporator or cold plate - probably around $2k
* adding addition battery capacity - probably $500
* adding solar & controller, - probably $1k-$1500
By the time I am done, this is really starting to get out of control. It has me really scratch my head and wondering what's wrong with buying a block of ice every day or two for the few weeks a year living in New England. The convenience would be very good, but you can never look at it from a financial payback in terms of saving money spent on ice or even increased value of the boat if it was sold - it is purely convenience & independence.