I once heard a knowledgeable captain compare maintaining a large, traveling sport-fishing boat to running a small city. And even though that analogy might be a bit of a stretch, it holds true to a certain degree — both require water and electricity management, fuel regulation and waste disposal. In short, you need to manage your resources to run a sound ship.

Keeping things cool aboard a boat during a long trip ranks as one of the greatest resource-management challenges any captain faces. Aside from keeping the engines humming and not running over a hooked fish, a good captain has to make sure that the beer is cold and that there's enough ice on board for the rum drinks at the end of the day. 
 
When you think about it, there are a lot of things on board that you need to keep cool, including your guests via air conditioning, the vessel's refrigerated fresh food supply and the food and/or bait in the freezers — hopefully stored in separate units so your hamburger doesn't taste like a ballyhoo.
 
Although most boats come equipped with refrigerators and freezers these days, it wasn't that long ago that many boats simply came with a chill box consisting of nothing more than a custom-made cooler that held a day's supply of ice. Once boaters discovered the limitations of fishing with a cooler, they started building their own custom cooling units from household refrigeration equipment.

These early systems proved temperamental at best, requiring frequent repair, a lot of maintenance and usually a premature replacement. To compound the problem, most crews mounted the compressor in the boat's engine room, a hostile environment combining a steady diet of heat and salt spray — a concoction that proved deadly to early equipment.
 
But as with all things marine, clever engineers soon began to design marine refrigeration units from scratch. As a result, marine refrigeration units became more reliable, spawning a huge increase in the number of refrigerators, freezers and air-conditioning units found on standard equipment lists.
 
Lots of companies manufacture basic marine refrigeration units and even the basic ones work well. All of them operate using a combination of a compressor and a condensing unit that circulates pressurized refrigerant through copper tubing. The copper tubing usually runs through metal cases called chill plates, which become extremely cold, drastically lowering the temperature in the space you want to cool. By regulating the size of the plate and the amount of coolant flowing through it, you control the temperature.
 
You'd be hard-pressed to find a convertible sport-fisher that comes without a wide range of refrigeration devices as standard equipment — with several high-tech options thrown in for good measure. Fortunately, the new generation of refrigeration systems offers greater flexibility than ever before in terms of mounting options and storage capacity. Basically, if your boat has a space that can be chilled, there's a custom chiller unit available to keep it cool.
 
As these newer units turned to advanced technology for better reliability, they gained greater efficiency and improved temperature controls in the process as well. The latter issue is no small matter. On an older Bertram I once owned, the ancient marine air-conditioning units either blew warm, muggy air or an arctic-like blast that would make the salon suitable for hanging raw meat in about a half-hour. The temperature adjustment was so sensitive that you could never get it right. Now, digital controls make hyper-accurate temperature control as easy as turning a dial.

Glacier Bay is one of the companies on the forefront of these modern designs. The company's Micro Hybrid Plate System (a DC or direct-current system) works via an innovative brushless rolling piston compressor, which is both quiet and highly efficient. It weighs less than 12 pounds but provides seven times the refrigerating capacity of most other DC compressors. It's hermetically sealed, and you can run refrigerator, freezer and air-conditioning units off one compressor. Glacier Bay's patented Arctic-Air option adds AC by simply attaching a module to the refrigeration lines.  
 
Most of the refrigeration equipment designed to cool larger spaces requires AC power. For instance, Technicold makes a series of rugged chill plates called "hold over" plates, which can be ordered in 115- or 220-volt options, or you could even use engine driven power if you're really serious about your refrigeration needs.