Looks like you plan on doing a lot of fishing in the future HG. I reckon you could fit a couple of thousand dollars worth of fish fillets in a box like that.
The compressor unit looks to be very good quality as it should be if it is a Danfoss.
If you wanted to you wouldn't necessarily have to use that evaporator plate. I am sure that unit could run a couple of eutectic plates.
The most important part of a marine fridge is the cold box. If it has to be built in it is worth paying for the very best insulation and professional fibre glassing.
The shape of the box will then dictate what you use as evaporators.
That evaporator looks like it would be very efficient but I think it could puncture easily if it does not have a guard plate. It, by it's nature needs to be fixed to the side of the box whereas eutectic plates can be mounted like dividing panels across the box which allows them to draw heat from the products on both sides rather than trying to draw it through the side of the box.
You could be up for as much in solar panels and battery to run it as what the fridge costs.
You are doing a great job on this restoration HG. Only the best gear going into her.
. I sort of figure on dropping into Bowen when the veggies are harvesting and Blanche and freeze as much as I can and add fish along the way. Unfortunately for me I have a middle ear problem so I cant drive to much depth these days so its snorkeling only for me 
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