when i bought my boat i also had a crosby engine
drive / 120 volt system. it ran two holding plates, one for the freezer and one for the fridge. the freezer was about 4 cubic feet, the fridge about 6. but it wasn't working, and a bill from a previous repair i found on the boat was for over $1000. after a bit of research
i decided to make a big change.
the problem with the previous system is that it had to be run every day, maybe twice a day, to charge the holding plates. that meant that if i were anchored out i would have to be on the boat every day to run the engine. it also occupied a large space in the engine room and was something of a mechanical monster. after much thought i simply ripped out the entire system and installed an adler barbour 12 volt air cooled system.
i put the adler barbour in the box that used to be the freezer. the former fridge box is now both fridge and freezer. after some years of actual usage i've found that the fridge was too big, so i filled the bottom with removeable insulation
and it's now about 3.5 cubic feet. i can easily remove the insulation
if i have some need for a larger fridge. and it now runs off the battery
bank which means it runs without any attention from me, for as long as there is juice in the batteries (think solar panels
i see you live in palm coast. i'm right down the road in daytona beach. my boat is currently in titusville but i'm bringing it up to daytona halifax
harbor marina in a few weeks. maybe we can get together and i can show you what i did.
is much easier than you might suppose.