Marine Corps Mechanics - MOS 3521

Marine Corps Mechanics (MOS 3521)

Marine Corps Mechanics (MOS 3521), or Automotive Maintenance Technicians, work on motor transport equipment.

The job requires the servicing, inspecting, maintenance, and repairs of every type of military vehicle.

Marines depend on mechanics to have reliable transport that will not leave them stranded in dangerous situations.

Learn more about the job duties, required training, and civilian job outlook for Marine Corps Mechanics (MOS 3521).

Education, Qualifications, and Training

3521 mos marines
Marine Corps Mechanics (MOS 3521) are trained on a variety of motor vehicles and military equipment. Image:

Mechanics (MOS 3521) are one of the many jobs under Marine Corps Occupational Career Field 35 – Motor Transport.

The primary Military Occupational Specialty (MOS) is reserved for Marines between the ranks of Private (E-1) and Sergeant (E-5).

Are you interested in becoming a mechanic for the Marine Corps?

There is education, qualifications, and training required to join the Marines and work in MOS 3521.

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Marines are required to have a high school diploma or GED in order to enlist in the military branch.

It also doesn’t hurt to have some college credits under your belt as many Marines join the force with an average of 15 credits.

While not mandatory, it helps if you have a background in mechanics or vocational training, especially experience working on vehicles.

All new Marines must complete the Armed Services Vocational Aptitude Battery (ASVAB).

The series of tests determine eligibility for a variety of Military Occupational Specialties, including MOS 3521.

Marine Corps Mechanics (MOS 3521) must score 105 or higher in Mechanical Maintenance (MM) and 100 or higher in Electronics (EL) in order to qualify for the MOS.


There are some unique qualifications of Marine Corps Mechanic (MOS 3521).

The Marine Corps designates minimum and maximum height requirements in order to operate on vehicles.

Soldiers must have a minimum height of 59 inches and not exceed the height of 75 inches.

MOS 3521 Mechanics must have normal color vision (no color blindness).

The Marines will test for acuity, color, field of vision, and depth perception.


New recruits, even those that are not selecting a combat MOS, must endure boot camp.

Boot camp, or Marine Basic Training, lasts 13 weeks and will push your limits from a physical and mental standpoint.

After surviving boot camp and Marine Combat Training, you can begin to focus on your Military Occupational Specialty (MOS).

Marine Corps Mechanics (MOS 3521) are required to complete the Automotive Organizational Maintenance Course (AOMC).

The instruction takes place at the Marine Corps Combat Service Support School at Camp Lejeune in North Carolina.

Marines with ranks E-4 (Corporal) and E-5 (Sergeant) can receive skill enhancement training through the Motor Transport NCO Course.

The course also takes place at Camp Lejeune in North Carolina.

What does a Marine Corps Mechanic Do?

marine corps mechanics
Marine Corps Mechanics service motor vehicles like the Humvee. Image: 3rd Marine Aircraft Wing

Mechanics (MOS 3521) service, inspect, maintain, and repair motor transport equipment for the Marine Corps.

The role of an Automotive Maintenance Technician (MOS 3521) is high priority since other soldiers depend on mechanics to provide reliable, consistent operating motor vehicles.

Motor vehicles and equipment that break down in the field pose a serious risk for soldiers trapped until repairs are made.

Consequently, Marine Corps Mechanics often work in high-risk circumstances, especially in combat situations where quick yet effective repairs are essential.

Marine Mechanics are not your average grease monkey and are exceptional at diagnosing and making timely repairs.

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Job Duties of MOS 3521 Mechanic

Though the majority of your time as a Marine Corps Mechanic is spent working on engines, you also have other job duties.

Automotive Maintenance Technicians also conduct convoy operations and assist with movement control.

There is a need to establish a tactical motor pool when the situation calls for the procedure.

Mechanics may handle refueling operations for the motor pool to assist other members of the battalion.

It is the responsibility of Marine Corps Mechanics to ensure all vehicles used in the field are inspected and maintained in top condition.

Marines that serve MOS 3521 also manage parts and other inventory including tools and supplies.

The shop is regularly cleaned and maintained, and hazardous materials are properly disposed of.

When an issue with a military transport vehicle arrives, the mechanic is skilled to troubleshoot a wide range of problems from the transmission to cooling, steering and braking, electrical to mechanical. 

Marine motor vehicles receive quite a punishment in the field, and mechanics are what keep them operable under intense conditions.

What does a Marine Corps Mechanic make?

usmc mechanics
The civilian job outlook for Marine Mechanics (MOS 3521) is very optimistic. Image: Wikimedia Commons

The work you perform as a Marine Corps Mechanic (MOS 3521) is essential to the daily functions of the military branch.

However, you will not receive pay in the military based on your Military Occupational Specialty (MOS).

Pay in the Marine Corps is determined by your military rank and years of service.

You can get an average idea of what you will earn each month by studying the following table based on Marine Corps rank:

InsigniaPay GradeRankAbbreviation2023 Minimum Monthly Pay
E-1 +4 monthsPrivatePvt$1,917.60
E-2Private First ClassPFC$2,149.20
E-3Lance CorporalLCpl$2,259.90
E-6Staff SergeantSSgt$2,980.50
E-7Gunnery SergeantGySgt$3,3445.80
E-8Master SergeantMSgt$4,957.20
E-8First Sergeant1stSgt$4,957.20
E-9Master Gunnery SergeantMGySgt$6,055.50
E-9Sergeant MajorSgtMaj$6,055.50
E-9Sergeant Major Of The Marine CorpsSgtMaj$6,055.50


The U.S. Armed Forces are known for the benefits provided with a monthly salary, including:

  • Medical Insurance
  • Affordable Life Insurance
  • Vacation Time
  • Special Pay
  • Retirement
  • Education: Marines can earn full tuition, merit-based scholarships, allowances for books and fees, plus an annual stipend for living expenses.
  • Housing: Allowances for living expenses, utilities, and maintenance.
  • Food: Allowance for the on-base dining hall and access to tax-free department and grocery stores.

Job Reviews

There are a variety of job reviews about what it is like to serve the Marine Corps as a Mechanic/Automotive Maintenance Technician on

The common term many former MOS 3521 use is “fast-paced work environment” and “challenging”.

However, the skills and experience you receive in the Marines will not only suit you well for a military career but also civilian life after finishing service.

At the end of the day, the Marine Corps is not for everyone.

Military life is demanding and as one poster put it, you must have “thick skin”.

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Civilian Job Opportunities

There are many Marine Corps Mechanics (MOS 3521) that enter the military career with some previous experience working in the industry.

At the very least, many grew up working with their dad or another mentor maintaining and repairing vehicles.

Therefore, combined with the training and experience you receive in the Marine Corps, you are well prepared for civilian employment as a mechanic.

Countless auto shops love to hire former Marines that worked in the military as mechanics.

Your expertise on unusual, military-specific motor vehicle equipment goes a long way in being able to diagnose and repair just about any type of engine.

Some former MOS 3521 work at auto shops while others perform work as mechanics for dealerships.

Trucking companies and airlines also will actively seek former military because of the unique skills and the expertise of its mechanics.


Mechanics, or Automotive Maintenance Technicians, serve a high-priority MOS within the Marine Corps.

Marine Corps Mechanics (MOS 3521) are responsible for the service, inspection, maintenance, and repairs of all related motor transport equipment.


Levi D.
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