Due to unparalleled quality and superior service backed by decades of experience, we have chosen R.W. Fernstrum & Company to cool our equipment and are happy to pass along our OEM buying power for not only dissipating your HVAC heat load, but also your power plant and generator equipment.

Rather than pump corrosive raw water through your equipment for cooling, install a keel cooler – you will extend your components life and never again have to clean a plugged strainer! Ideal for shallow coastal waters where seaweed, algae, mud, sand, and silt are a constant problem. These coolers can be surface mounted, recessed or side-mounted and have very little drag when properly installed.

Call us with your particular cooling needs and we will be happy to provide you with a very competitive quote.

You can eliminate your troublesome water pump completely if you use a dry exhaust system, and actually, have no raw water in your vessel at all!

Surface mounting on an existing hull with a wedge-shaped fairing block as shown will not only protect the cooler from striking an object but reduce the drag to an almost nonexistent level.
Recessed mounted coolers offer the best protection, especially when hauling your vessel, and in new construction, this is the preferred installation.
For a shallow draft vessel, you may mount the cooler on either the side or stern of the vessel in a recessed or surface mounted installation. For HVAC cooling that is used dockside only, we actually mounted a cooler on the transom!
Side mount shown in a recessed compartment.
A BOX COOLER is one of our coolers mounted in a sea chest as shown. This offers you the best protection possible and gives you more flexibility for servicing and stacking multiple units in one compartment.

The unique Fernstrum design results in a smaller, more compact cooler for the same amount of heat rejection. The unique rectangular shape of our tubes provide a far greater surface area and negates the need for grooving, and our use of heavy gauge 90/10 CuNi we believe ends up in a far superior product.

So what does that do to the size of a cooler? In many circumstances, a kit cooler can be anywhere from 33% to 100%larger than a GRIDCOOLER based on the same cooling requirements. In addition, the sizing difference includes standard cooler loadings of 90% for a kit cooler and 75% for a GRID COOLER.

Fact & Fiction

About Keel Coolers, in Particular, the R.W. Fernstrum GRIDCOOLER
Fiction Fact
A GRIDCOOLER can't be used in high-speed applications. GRIDCOOLERS are currently being used on high-speed crew and patrol craft. The GRIDCOOLER creates a negligible amount of drag in high-speed applications, and their sturdy design will hold up under the most demanding conditions.
A GRIDCOOLER must be mounted in a recess. Any GRIDCOOLER may be mounted in a recess or just externally mounted on the side, bottom or rake of the hull, depending on the vessel design.
GRIDCOOLERS require too many through-hull fittings. Any GRIDCOOLER can use our L-Series option which requires only two through-hull fittings, one for the inlet nozzle and one for the outlet nozzle.
The GRIDCOOLER is more difficult to plumb than our competitors' coolers. The two-pass or U-Flow GRIDCOOLER has both inlet and outlet nozzles on the same end of the unit. The nozzles can use a variety of fasteners including hose connectors, flanges, or threaded pipe.
Grooved round tubing is more efficient than smooth rectangular tubing. This statement might be true, depending on the cross-sectional area and perimeter of the two tubes used in the comparison, but don't be misled into believing that the grooved tubing used by our competitors is more efficient than our tubing. The efficiency of the cooling units in question can be determined by simply comparing the size of one unit to the size of the other. If a GRIDCOOLER and a grooved tube cooler are sized for the same application, our GRIDCOOLER will be the smaller unit.
70/30 copper/nickel is more durable than 90/10 copper/nickel. If you are comparing apples to apples, 70/30 is only slightly more durable than 90/10 copper/nickel. However, in comparing our 90/10 to our competitors' 70/30, you may be comparing apples and oranges. Our 90/10 tubing is twice as thick as our competitors' 70/30. This increase in wall thickness more than makes up for any differences in material.
Welded and brazed joints can crack and leak. Unlike"O" ring slip joints which leak under vibration, welded and brazed joints will not crack and leak under normal operation, and many units damaged by severe groundings or being struck by debris will still operate effectively without leaks. In a heavy pounding sea, kit coolers and their gasket joints can easily fail.GRIDCOOLERS are built to withstand heavy seas.
Brazed coolers can't be bent to conform to a hull's curvature. Because of the ductile qualities of 90/10 copper/nickel and the inherent strength of brazed and welded joints, a GRIDCOOLER can be bent to meet your desired specifications.


Engineered Keel Cooling
Our 100% parts inspection process and rigorous testing procedures ensure that all raw material and every GRIDCOOLER is built with the same exacting standards that prompted the U.S. Navy to set their keel cooling standards by the Fernstrum GRIDCOOLER. Nearly 25% of the production time for every GRIDCOOLER is spent in inspection and testing, from raw material to finished product. This level of quality control ensures the dependability and performance that has kept our GRIDCOOLERSin service for as long as 30 years.
A standard series GRIDCOOLER is made of either heavy gauge 90/10 copper-nickel or 5000 series marine grade aluminum rectangular tubing. These alloys were chosen because of their resistance to saltwater corrosion and their heat transfer abilities. The copper/nickel units are silver brazed, and the aluminum units are welded. These construction materials and methods provide a level of durability far above any kit cooler.
While 70/30 copper/nickel is marginally more corrosion resistant than 90/10, its lower heat rejection abilities make it a relatively poor heat conductor when compared to 90/10. However, don’t be fooled into believing a kit cooler is more corrosion resistant than a GRIDCOOLER. A kit cooler uses a very thin-walled tube while our GRIDCOOLER uses a much thicker wall tube. This thicker wall tube, and our welded and brazed joints, led the U.S. Navy to give the Fernstrum GRIDCOOLER a 20-year rating.
Kit coolers use “O” rings and gaskets to hold their coolers together for a “tight” seal. Unlike a kit cooler, the welded and brazed construction of a GRIDCOOLER provides a solid cooler. Welded and brazed joint construction also eliminates the excess wear between vibrating tubes and fasteners that occurs with kit coolers. Sure, you can replace kit tubes a bit easier, but why should you have to replace tubes?
Every GRIDCOOLERis built out of high-quality pipe and sheet stock, not cheap out-of-round and threadbare castings or plug-and-pray seals. This allows us to let you decide how your GRIDCOOLER will attach to your vessel, and have peace of mind in knowing it will attach properly.
The GRIDCOOLER is the most efficient keel cooler available. Our 90/10 copper/nickel has 1/3 more heat rejection ability than the 70/30 copper/nickel used by the competition. Our rectangular tube is much more efficient than the thin spiral round tube used by the competition. The size of our cooler can be easily compared to any of theirs. Based on the same information, our GRIDCOOLER can be as little as half the size of their bulky kit coolers.
Overheating, uneven engine cooling and air pockets in the cooling system are just a few of the problems associated with excessive pressure drop in an engine cooling system. Any one of these problems will cause premature engine wear and engine failure if the problem is not addressed. It also limits the types of pumps that can be used for coolant flow. Unlike the kit coolers you may see, our GRIDCOOLER is designed to create a minimum amount of pressure drop. Kit coolers using spiral tube create turbulence and turbulence is a pressure drop. Kit coolers with only one through-hull fitting severely restrict water flow, which creates a pressure drop.
With over 8000 GRIDCOOLER models available, we can recommend a cooling system that meets the unique needs of your engine on your vessel in your operating environment. Our standard GRIDCOOLER models can use any one of our five tube types, they can have between 4 and 24 tubes and they can be between 21 and 187 inches long(in six-inch increments). If the standard configuration of a GRIDCOOLER creates a problem, we can make modifications as needed.
Unlike kit coolers, our units have a 75% heat rejection loading, giving a built-in safety factor of 25% for pump and impeller wear, internal and external fouling, re-powering, etc.
Designed to be externally mounted or flush-mounted on the hull, the GRIDCOOLER presents no greater problem than ordinary through-hull fittings. The GRIDCOOLER is a completely assembled unit ready for installation, complete with heavy neoprene gaskets for sealing the inside and outside of the hull. If needed, a GRIDCOOLER can be bent to conform to the hull’s curvature.
With over 50-years experience in the marine engine cooling market, we will engineer a GRIDCOOLER to meet your specific application and needs. We can give you advice on cooler placement, installation, and service. Should you require an emergency replacement unit, we can have it shipped to you within three business days or less.
Kit coolers might be available in as many as a couple of hundred models…GRIDCOOLERS are available in over 8000 standard models, and a near-limitless number of specials can be built for your individual application.
At up to twice the size, kit coolers create more drag than our GRIDCOOLER. After a combination of independent testing by the Vienna Model Test Basin and in-house testing was completed, it was proven that the Fernstrum GRIDCOOLER creates less drag than the difference in drag between spraying and rolling a coat of anti-foulant paint on a hull.
If a kit cooler is damaged, a catastrophic loss of coolant usually follows due to the loss of tubes. Our GRIDCOOLER does not suffer from this problem. Because we use brazed and welded joints, the cooler may leak, but any coolant loss should be replaced.