The original ‘refrigerator’ box on the Pearsons were designed to allow for a layer of ice blocks in the bottom with a drain to the bilge. This made for a box large enough to hide a side of beef!
It was so deep that we could not reach the bottom. Not very efficient for an actual refrigerated box. I divided the box into a ‘spill-over’ system with a small freezer box separated from the refrigerator box. I then built up the box with additional vacuum insulation panels and a lining of FRP panels. The system is driven by an evaporation panel cooled by a Frig-a-Boat compressor.
We decided that the most important thing was to increase the insulation as much as possible. So after removing the existing countertop of porcelain tile and the plywood substrate, I drilled 1/2″ holes at about 8″ spacing from the inside of the fiberglass box into the space around the box. It seems that the original box had a layer of sprayed foam around it which was then installed into the cabinet, this left a void of varying thickness to the plywood, I used ‘low pressure’
aerosol foam from Home Depot to inject into the network of holes. It was a bit hard to tell how much was enough since the foam tended to seek out the voids and then keep expanding. You can see by the photos that it found its way out! I used clamps th make sure the foam didn’t deform the cabinet. It was important to use the ‘low pressure’ foam.
Once the foam was set and trimmed, I began to build additional layers of insulation on th interior of the box. First was to add six layers of 1″ foil-faced polyiso foam board to the very bottom of the box for insulation as well as to make the bottom reachable.
I then added a layer of 1″ polyiso board to the walls on all sides. This was tacked in place with spray adhesive. I realy wanted to use some vacuum panels as they have crazy high R-Value. As i looked into it, I found them to also be crazy expensive if I ordered custom sizes. I was able to find some panels that I could incorporate from R Parts .
They have random size panels left over from other orders. I was able to put a few 1/2″ panels in place and fill in wit 1/2″ polyiso board. I then lined the entire interior with another layer of 1/2″ polyiso board, mostly to protect the vacuum panels from damage. If they get punctured, their value drops to zero.
Once all the insulation was in place, I partitioned the box into a small freezer box that would house the evaporator plate and a larger refrigerator box separated by a piece of 1″ ‘pinkboard’. This “spill-over” design came from Go2 Marine . I also bought the evaporator plate and controls from them.
The 2″ hole in the partition houses a low volume 2CFM fan. The idea is to let the freezer side fill up with cold air and spill over into the refrigerator side. The fan simply speeds the process but it needs to move the air very slightly.
The next step was to line the interior with FRP which was glued in place with spray adhesive. It was interesting to note that when spraying tha panels with adhesive the propane sensor on the stove went off which was a good reminder to be wearing a respirator!
Covering all the interior surfaces required some scribing and fitting but once everything was in place, I epoxied the corners with 2″ tape, let that cure and filleted the joints with thickened epoxy to make cleaning easier. The final step to complete the interior was to take a holesaw and cut a recess in the bottom of each compartment to allow a 2″ PVC cap to be glued in as a water trap. The thinking was to make it easier to clean by giving the water a place to accumulate.
As you can tell, this was a very labor-intensive project…I had forgotten how much so until now writing about it!
The next step was to build up the top and the openings with foam and FRP. I laid out the top to maximize the openings. I had originally planned to make the openings ‘stepped’ with corresponding steps in the lids. 
I soon realized that simply beveling the openings would be simpler and allow for a better seal.
I cut out the openings using a jig and plunge-cut router. The jig was sized for the finish openings in the Corian and shimmed in 1/2″ for the openings in the baltic birch substrate. Once the openings were cut, I flipped the top and built up the insulation with pieces of 1″ pinkboard cut to a bevel at the openings. 
The lids were made from the cut-outs and built up with pink board to match the bevel. I left about 1/2″ of space between the opening and the lid to allow for sealing gasket. Once all the pink board was shaped and glued in place with spray adhesive, I overlaid everything with FRP sheet.
This took a bit of careful fitting then the joints were sealed with white silicone caulking. I am not usually a fan of silicone but this was a good application. After taking everything to the boat to check for fit, I cut the Corian top 1/8″ smaller than the plywood top. The most important thing to remember about working with Corian is to relieve any stress points and not fit it too tightly. 
I then used the plunge cut template to cut the openings with a 1/8″ straight bit (carbide). I was able to get a very clean cut by feeding very slowly. After a bit of touch up sanding I rounded off the edges with a 1/8″ radius bit and finish sanded. I dapped (recessed) for the hinges carefully cutting to pencil lines. I used an oversize drill bit to drill for the hinge screws through the Corian. The screws do NOT thread int the Corian, only the substrate. The same is true for the holes around the perimeter. The wood fiddles around the edges are fastened to the substrate, not the Corian. Notice that all the inside corners have generous radius. Corian will crack at hard corners. Makes a beautiful top but is temperamental.
When trying to determine the best seal, I first tried a wide piece of soft closed cell foam. There was not enough “give” and the topswould not close. I ended up using some 3/4″ x 3/8″ weather strip with two bands around each door.
Once everything was complete in the shop, I took tha parts to the boat to install. After getting the insulated plywood top screwed down, I needed to seal the FRP box to the FRp on the bottom of the lid. Space was tight leaving no room to manipulate a caulking gun. I found an aerosol silicone with a long spout that was easy to use by feel.
Then it was just a matter of installing the Corian and the wood trim.
The system has worked really well so far. The only provlem being that even with the freezer turned to the lowest setting and the spill-over fan on low, some of the food in the refrigerator side are freezing. Good problem to have bearing in mind that we are still in the cold water San Francisco. We’ll see how it is as we get into warmer waters in Mexico. One thing we discovered is that even with the double seal we were getting some condensation around the lids. We solved this by placing large silicon baking sheets over the openings to seal the moisture out.
It is great to have a supply of ice for drinks and room to freeze extra fish! The compressor only draws around 3 amps so it is easy on the energy budget. Solar has had no problem keeping up with our needs except for the sunless days from Everett, WA to San Francisco.