Leading, not imitating.

Our commitment to quality means you get a reliable, long-lasting cooling system from the pioneer of the rectangular tube keel cooler. Since 1949, each marine heat exchanger is engineered to meet the requirements of your engine, vessel, and operating conditions.

The GRIDCOOLER Keel Cooler has continually evolved to meet the requirements of naval architects and the marine industry worldwide. Our team of craftsmen employ the latest technologies to enhance our manufacturing process. The result is a custom-designed GRIDCOOLER Keel Cooler that exceeds expectations.

Contact our sales and engineering team for expert advice on cooler sizing, placement, installation, and service.

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Design Features

One-piece Header Design
Fernstrum has continually evolved the GRIDCOOLER Keel Cooler’s design to improve efficiency and dependability. The rectangular one-piece header design has fewer joints for improved durability and provides greater flexibility in custom cooling solutions.
Marine ApplicationsStationary ApplicationsHow Keel Cooling WorksGRIDCOOLER Keel Cooler Manuals & Catalogs

Installation Options

Our expert engineers and sales team will help you determine the best installation solution. Please note the operating conditions and hull design of a vessel weigh heavily on how a unit is installed. Described below are a few common installations for a GRIDCOOLER Keel Cooler.


Recessing a GRIDCOOLER Keel Cooler streamlines the installation and provides significant protection from potential damage. Independent tests conducted at the Vienna Model Test Basin have shown that drag is negligible when the unit is recessed into a ship’s hull. The position of the recess can be located on the side or bottom of the hull. This type of installation is common in new projects and ideal for fast-moving vessels.


An external installation typically applies fairing and side plates for added protection and to improve streamlining. This mounting option is commonly used in retro-fitting projects.

Side Mounted

Mounting the GRIDCOOLER Keel Cooler on the side of the hull prevents potential damage to the unit. It is ideal for situations where a keel cooler cannot be mounted to the bottom of the hull. Note: When recessing the unit into the side of the hull for generator sets and/or equipment operating at dockside, angle the top of the recess box to allow convection current over the cooler.

Material Options

Premium materials to help maximize your cooling system

The GRIDCOOLER Keel Cooler is a completely assembled unit and is factory tested to ensure dependability. The rectangular shaped tubing used in its construction is structurally sound and provides a higher heat transfer rate than round tubing.

90/10 Copper-Nickel
The copper-nickel GRIDCOOLER Keel Cooler is crafted using heavy-walled rectangular 90/10 copper-nickel tubing. This alloy was selected based on its durability, heat exchange abilities, resistance to saltwater corrosion, and natural antifouling capabilities.

5000 Series Aluminum
The aluminum GRIDCOOLER Keel Cooler is designed specifically for unpainted aluminum hull applications in fresh or cold seawater environments. 5000 series aluminum alloy was selected based on its compatibility with unpainted aluminum hulls and saltwater corrosion resistance. The alloy compatibility between the hull and keel cooler prevents pitting and avoids potential damage from interacting metals. Aluminum units are tig welded for durability.

Configuration Options

The GRIDCOOLER Keel Cooler is sized to meet your engine’s cooling requirements and operating environment. Our team will work with you to recommend features to optimize the functionality of your cooling system. The following examples show a few of the more common configurations. Additional configurations are available upon request.

Enhanced & Smooth Interior Walled Tubing
Fernstrum offers two types of surfaces on the interior of the copper nickel tubing, smooth or enhanced. The enhanced surface, a Fernstrum exclusive, is a truncated cone pattern on the interior of the tube generating greater heat transfer. Compared to a smooth walled tube, the enhanced tube increases the heat transfer capability by up to 30 percent. This is especially true in applications where glycol solutions are utilized. The improvement in efficiency may reduce the number or size of the units required for an application. Note: The interior surface of the tubing is determined based on your cooling requirements.

When faced with limited space or larger cooling requirements, a stacked GRIDCOOLER Keel Cooler reduces the footprint of the keel cooler while providing greater heat transfer. The design is ideal for cooling larger engines, reducing the number of units required, or fitting into an existing application in the case of repowering.

Angled Tube
An angled tube GRIDCOOLER Keel Cooler optimizes the heat transfer for side mounted zero knot or stationary applications. The design exploits the natural convection current created by the heat exchanger. The unique position and angle of the tubes are crafted to maximize the flow of raw water between the tubes. This configuration also resists the collection of silt and other debris from building up on the unit.

The angled tube GRIDCOOLER® Keel Cooler’s tubes are positioned to enhance and exploit the natural convection current generated by the heat exchanger.

Single- & Multi-Pass Designs
Fernstrum offers a range of single and multi-pass designs to help optimize your cooling solution. These designs maximize the efficiency of the engine coolant flow, allowing for a more compact solution.

E1 Option

E1 Option units place the zinc anodes and drain plugs on the end of the keel cooler reducing the hull projection; a benefit to high speed craft and fishermen when entanglement of nets and/or lines is a concern.

HD Option
HD Option stiffener plates can be added to units providing additional support to prevent tubes from bowing, bending, or vibrating from the impact of heavy seas. These plates do not have additional mounting points. The HD Option is ideally suited for applications where the vessel is operating in heavy pounding seas, strong currents, or the keel cooler is positioned near the bow of the vessel.

L Option
L Option support plates are designed to minimize intermediate support bolt hull penetrations. These support plates extend beyond the keel cooler side tubes, providing additional securing options. This feature is especially useful in retrofitting a keel cooler to an existing vessel.

Z Option
Z Option flanges relocate the connecting and mating points to the hull’s exterior, eliminating hull penetrations. The typical through-hull nozzle mounting connections are replaced with a flange. Mating flanges are provided in carbon or stainless steel. Additional mounting hardware is also supplied for isolation. This design is ideal for installations where mounting hardware cannot be easily accessed from the interior of the hull, easing installation on double hulled vessels and may eliminate the need for cofferdams. L Option support plates are standard in this configuration.

Use Gridcooler® Configurator


PO Box 97 • 1716 11th Avenue
Menominee, MI 49858 USA

Phone: 906-863-5553

Fax: 906-863-5203

Email: sales@fernstrum.com


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