Waterproof Navy and Marine Corps Radio Jeeps

A Brief History of 1940s Waterproof Navy and Marine Corps Radio Jeeps.

by Fred Coldwell

Willys developed the first WW II era purpose-built radio jeep in fall 1942 at the request of the Navy, which was looking for a small light weight vehicle to carry 12 volt mid-range command radio sets during the Pacific island-hopping campaign. The WC 3/4 ton Dodge 12 volt radio command car and carryall were too large and heavy for swift water borne invasions, so Willys took the 12 volt 55 ampere Auto-Lite generator that powered the Dodge electrical system and installed it as an auxiliary generator in the 1/4 ton 4x4 MB jeep. This generator mounted between the driver and passenger seats and charged two 6 volt batteries wired in series that were installed immediately behind each front seat. This auxiliary generator resided in its own housing and was driven by a fan belt powered by a full-time PTO mounted on the rear of the jeep transfer case.

These MB radio jeeps were manufactured by Willys throughout WW II and received different model designations as the jeep itself evolved during the war: the NOM-12, the MZ, MZ-1 and MZ-2. The Auto-Lite 12 volt auxiliary generator was also available in kit form that could be installed in any standard MB or GPW jeep to convert it into a non-waterproof 12 volt radio jeep. These WW II auxiliary generator kits evolved into the postwar MX-736/MR Power Supply Kit.

Between the seats generator and battery boxes.

Beginning in July 1944, to reduce radio interference from the jeep’s ignition system, the MZ-2 radio jeep began using ignition system suppression parts manufactured by Hallett Engineering, Inc. in Englewood, Calif. The suppression parts were mostly cast aluminum boxes and housings that fit around standard MB ignition system parts to restrict transmission of their electrical signals and static. Although these Hallett aluminum boxes and casting were tight-fitting, they were not waterproof.

The MZ-2 used the late WW II dustproof distributor and the standard model W.O. carburetor. The real challenge will be finding any of the original Hallett ignition suppression parts that shielded the standard MB ignition system. Those Hallett parts were removed and discarded either when a Deep Water Fording kit was installed in the late 1940s or by later owners if present only to be replaced by standard jeep ignition system components for which maintenance parts could be found and bought. Finally, because all Hallett parts were removed when any radio jeep was upgraded with a postwar waterproof Deep Water Fording kit, very few Hallett aluminum ignition system suppression parts have survived. It is very challenging today to find Hallett parts.

As the Pacific campaign unfolded, the Navy and Marine Corps found they had to waterproof their jeeps in the field to be able to travel from landing craft to shore with stalling out or drowning. At their request, Willys in 1943 developed a partial deep water fording kit contained an exhaust pipe extension and asbestos goop that was applied to the standard jeep ignition system to waterproof it. A straight extension pipe going straight up from the carburetor through a hole in the hood provided the jeep’s intake air. But this was only a temporary field fix for a continuing island invasion problem.

So in January 1945 Willys began designing the first factory built waterproofed radio jeep called the MB-Navy Basic (MB-NB). It would have the auxiliary Power Supply kit and a complete Deep Water Fording Equipment kit installed on the factory line. Fording equipment included waterproof Auto-Lite ignition system components and air intake and exhaust extensions. This jeep continued using the standard WW II Carter W.O. carburetor that was waterproofed by having a two-piece aluminum housing installed around it. That awkward housing continued in use into late 1946.

Waterproof carburetor housing.

Very few, if any, MB-NB jeeps were completed or delivered by Willys before August 15, 1945. The earliest date codes found on any Auto-Lite waterproof ignition system components are from July and August 1945, and it seems few, if any, of these waterproof ignition system components reached the factory production line before WW II ended on August 15, 1945. It appears only around 300 MB-NB waterproof radio jeeps were delivered to the Navy after WW II, from August 15, 1945 to late March 1946. The only Navy/Marine Corps radio jeep produced from January to July 1945 was the non-waterproof MZ-2. The only movement towards better deep water performance was one made to its 12 volt 55 ampere auxiliary generator, which was upgraded in mid-February 1945 to become water-resistant by using brass bushings in place of steel bushings.

The waterproof Auto-Lite jeep ignition system components -- generator, voltage regulator, distributor along with Champion aircraft spark plugs -- continued to be manufactured during 1946 and 1947. In late 1947, Willys used many of these components to produce 1,000 Deep Water Fording kits MX-735/MR for the Navy. These kits also used the new Carter YS-637S waterproof carburetor, which replaced the standard WW II Carter model W.O. carburetor. Many of these 1947 kits were retrofitted on WW II Navy and Marine Corps radio jeeps to bring them all up to the latest standards.

Waterproof Auto-Lite ignition system.

In 1949 Willys revised the Deep Water Fording to a new standardized kit, MX-735A/MR, by replacing the Auto-Lite ignition system components with Bendix-Scintilla components that used fewer connecting cables. Besides being installed in the field on existing radio jeeps, these new waterproof Deep Water Fording parts were also installed on the factory production line on CJ-V35/U jeeps. And in 1952, all remaining Marine Corps radio jeeps which had not yet had the Bendix-Scintilla ignition system components installed were ordered to be upgraded with them so they all shared the latest waterproofing ignition system parts.

Bendix-Scintilla distributor with integral coil.

For these reasons, today there are only a few WW II Navy or Marine Corps radio jeeps that have survived in their original configuration, with just the 12 volt 55 ampere auxiliary generator between the seats and without having the postwar waterproof MX-735/MR or MX-735A/MR kits installed along with a mouse hole cut into their hood.

Unfortunately for us today, many of the deep water fording components from either Deep Water Fording kit (primarily the waterproof distributors and often the YS carburetor) have been removed over time and replaced with a standard MB/GPW distributor and model W.O. carburetor to facilitate obtaining maintenance parts. The YS carburetor was also used on the CJV-35/U and M38 jeeps so it remains available today. However, the waterproof ignition system components, whether Auto-Lite or Bendix-Scintilla brand, are far more difficult to find. Yet some do surface over time. It just takes patience, persistence and much good luck to find them.

Carter YS-637S waterproof carburetor.

The Great Willys Picnic | The CJV-35/U Page