Marine Corps Job of Auto Mechanic

These Marines Get the Corps Where It Needs to Go

Marine HUMVEE and amphib drop onto Somalia
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Making sure the Marines can quickly get where they need to be while in the field is obviously a high priority and an important job. The Marine Automotive Organizational Mechanic, which is military occupational specialty (MOS) 3521, makes sure all vehicles used in the field are inspected, maintained and in top condition.

This role requires these Marines to be ready to repair vehicles under a variety of conditions, including combat situations. It's definitely not a basic grease monkey job but will build on the mechanical skills many Marines have before they even enlist.

This is just one of the many jobs in the Marine Corps Occupational Career Field 35 (Motor Transport). It's considered a primary MOS, meaning it's reserved for Marines holding ranks from Private to Sergeant.

While the majority of your time will be spent working on engines if you enlist in this job, MOS 3521 is also responsible for conducting convoy operations, movement control, and establishing a tactical motor pool in certain field situations. These Marines also oversee refueling operations for the motor pool.


As the title suggests, Marines in this job oversee the repair and maintenance of all of the Corps' motor transport equipment. This includes all units of the Marine Air-Ground Task Force (MAGTF). These Marines service fuel and water tankers, seven-ton trucks, and the High Mobility Multipurpose Wheeled Vehicle (HMMWV) - also know as the HUMVEE. 

The Marine mechanic also is responsible for the safe operation of the mechanics' shop, storage of tools, storage of hazardous materials (fuels, lubricants, batteries) and troubleshooting vehicle failures. This includes all of a vehicle's systems, such as transmission, steering, cooling, braking, and electrical.

Replacing complete engines and transmissions are also part of the job. 

Much of what these Marines do falls under the category of troubleshooting, to make sure all vehicles can withstand the punishment they'll undoubtedly receive in the field. 


A Marine seeking this job should have a deep interest in motors and mechanical systems. While it's not required that Marines in this MOS have experience working on civilian motor vehicles, such experience is definitely a plus. 

You will need a score of 95 or higher on the mechanical maintenance (MM) segment of the Armed Services Vocational Aptitude Battery (ASVAB) tests and must complete the Automotive Organizational Maintenance Course. This test is given at Camp Lejeune in North Carolina

Similar Civilian Occupations

With the trainingand on-the-job experience you'll gain in this job, you'll be well-positioned for a variety of civilian careers. You can work as a mechanic in just about any auto shop or vehicle dealership, and you should have no trouble finding jobs at trucking companies.

Some Marines may even be qualified to teach at trade schools once their tour is ended. While this will require additional training and licensure, the discipline and focus Marines learn and hone while in the Corps makes them well-suited to train others.