We have an ice box and use it more as a pantry.
We plan our menus to reduce the amount of stuff that needs to be refrigerated.
For the things that need to be cold, I have a 3-way cooler (Mobicool
) We run it from shore power when possible. We can run it through the batteries if we are doing a lot of motoring (it was left plugged in the first time we used it and it drained our house battery in one night.) You can run it with propane, but, as the cooler is in the cabin we don't do this.
Once de-powered the cooler keeps things cool for at least 2 days (if you plan your opening/closings well).
For our weekend getaways we find this cooler to be more than adequate. When I go off for three or four days by myself the cooler keeps my Guinness at a good temperature.
We bungy the cooler at the end of the quarter birth opposite the galley. One heavy duty shock cord into two eye-hooks keeps the cooler secure. The bungy is placed horizontally to allow access to the cooler without having to mess around with it. We have been out in some pretty big waves (3 metre) and have had some pretty big heels (45 degrees) and the cooler has remained secure.
We have used this cooler for two seasons now and still think it was a great, inexpensive, low PITA solution to keeping food cool.
For longer trips (over 3 days) we use a 5-day cooler with dry ice. With food packed strategically we have kept steaks and shrimp etc. frozen solid for over 5 days.
One of the things about the ice box is that the ice block takes up quite a bit of your storage space. You also have to drain the box into your bilge.
I hope this helps.