Navy Machinist’s Mates, Non-Nuclear, Submarine Auxiliary (MMA): Definitive Guide (2025)

This guide provides helpful information for those looking to join the Navy as a Machinist’s Mate Auxiliary (MMA) during the Fiscal Year 2025.

Some say the reactor is the heart of a submarine—but without A-Gang, nobody’s surviving down there.

As a Machinist’s Mate Auxiliary (MMA), you keep everything running, breathable, drinkable, and livable.

Oxygen, water, heat, hydraulics, high-pressure air, diesel engines—if it moves, pumps, or powers the sub, you’re on it. While the crew handles the mission, you keep the boat alive.

ENLISTMENT BONUS: Future Navy MMAs are currently eligible to receive up to $10K in cash bonus just for signing up.

Job Description

navy-mma-insignia
MMA Insignia – Credit: U.S. Navy

Machinist’s Mates, Non-Nuclear, Submarine Auxiliary (MMA) are Navy enlisted Sailors who operate, maintain, and repair various equipment and systems onboard submarines. This includes damage control equipment, internal combustion diesel engines, hydraulic systems, atmosphere control equipment, refrigeration systems, compressed air and gas systems, water systems, and sanitary and plumbing systems.

MMAs keep submarines livable and operational. No oxygen? No mission. No drinking water? Game over. A-Gang makes sure everything works.

Where They Work

  • Mostly on submarines – U.S. and international waters.
  • Occasional shore duty, but the job is mostly at sea.
  • Work in auxiliary spaces, often with minimal supervision.

Key Responsibilities

  • Generate and store oxygen. No air, no crew.
  • Remove carbon dioxide, carbon monoxide, and hydrocarbons from breathable air.
  • Maintain and repair emergency diesel engines, watertight doors, hatches, masts, and antenna hoists.
  • Fix, replace, and inspect onboard equipment – valves, pumps, filters, compressors, hydraulic and pneumatic systems.
  • Operate and repair refrigeration units and water desalination plants.
  • Maintain air conditioning and galley equipment.
  • Log and analyze machinery records and reports.

MMA is a hands-on, physically demanding role. You work in tight spaces, with heavy machinery, under pressure. If it breaks, you fix it. If it fails, the whole sub feels it.

Different Roles in MMA

Auxiliary Equipment Manager

Keeps everything running, makes sure the right people are doing the right work.

  • In charge of hydraulic power plants, diesel engines, atmosphere control, sanitation systems.
  • Manages oxygen generation, compressed gas systems, submarine salvage equipment.
  • Trains and supervises the crew keeping things operational.

Auxiliary Equipment Operator

The one turning the wrenches, running the systems, making sure nothing breaks.

  • Operates diesel engines, firefighting systems, emergency dewatering, air conditioning, and more.
  • Keeps water, air, and power systems functioning.
  • Knows electrical safety, steam propulsion, hydraulic power plants.
  • Fixes leaks, replaces valves, fabricates parts, whatever needs doing.

Auxiliary Equipment Technician

If something’s broken, they figure it out and fix it.

  • Maintains hydraulic power plants, oxygen generators, freshwater systems.
  • Oversees system operations, making sure everything is working as it should.
  • Keeps maintenance records, tracks repairs, logs test results.
  • Diagnoses and repairs failures before they turn into bigger problems.

Everyone in A-Gang has a job. If systems fail, there’s no backup crew—just them.

Rank Structure

Pay GradeRateAbbreviationTitle
E-1Seaman RecruitSRSeaman Recruit
E-2Seaman ApprenticeSASeaman Apprentice
E-3SeamanSNSeaman
E-4Machinist’s Mate Auxiliary Third ClassMMA3Petty Officer Third Class
E-5Machinist’s Mate Auxiliary Second ClassMMA2Petty Officer Second Class
E-6Machinist’s Mate Auxiliary First ClassMMA1Petty Officer First Class
E-7Chief Machinist’s Mate AuxiliaryMMACChief Petty Officer
E-8Senior Chief Machinist’s Mate AuxiliaryMMACSSenior Chief Petty Officer
E-9Master Chief Machinist’s Mate AuxiliaryMMACMMaster Chief Petty Officer

Salary and Benefits

Salary for the First 6 Years

Monthly pay for Navy enlisted Sailors (E-1 to E-6) in the first six years is laid out in the January  2025 Active Duty Pay chart:

Pay GradeLess than 2 YearsOver 2 YearsOver 3 YearsOver 4 YearsOver 6 Years
E-1$2,108.10$2,108.10$2,108.10$2,108.10$2,108.10
E-2$2,362.80$2,362.80$2,362.80$2,362.80$2,362.80
E-3$2,484.60$2,640.60$2,800.80$2,800.80$2,800.80
E-4$2,752.20$2,892.90$3,049.80$3,204.30$3,341.40
E-5$3,001.50$3,203.70$3,358.80$3,517.20$3,763.80
E-6$3,276.60$3,606.00$3,765.00$3,919.80$4,080.60

Extra Pays and Allowances

  • Housing Allowance (BAH): For members living off-base. Covers rent, based on rank, location, and if they have dependents.
  • Subsistence Allowance (BAS): Enlisted get $465.77 monthly for food.
  • Hazard Duty Pay: For dangerous jobs. Pays $150-$250 per month, depending on the job.
  • Sea Pay: For those assigned to ships or deployed units. Depends on rank and time at sea, from $50 to $750 a month.
  • Submarine Duty Incentive Pay (SUBPAY): Up to $1,000/month based on qualifications and assignment.
  • Special and Incentive Pays: Bonuses for certain roles, like air traffic control or unique skills. These can be a few hundred to thousands per year.

Source: Figures are from the Defense Finance and Accounting Service.

Benefits

  • Healthcare: Active-duty personnel are eligible for free complete medical and dental treatment. Tricare programs are inexpensive for families to use.
  • Housing Accomodation: Depending on location, rank, and family size, free on-base accommodation or a tax-free housing allowance (BAH) for off-base living are available.
  • Food: Monthly Basic Allowance for Subsistence (BAS) for food costs is known as the “food allowance.”
  • Blended Retirement System (BRS): Conventional pensions are no longer available to active-duty personnel. Rather:
    • Thrift Savings Plan (TSP): Up to 5% in government matching and automatic contributions.
    • Retirement Pay: After 20 years of service, you’re eligible for monthly payments according on the BRS formula, which combines TSP savings with a calculated pension.
  • Education:
    • Availability of tuition assistance programs that pay for all or part of college tuition.
    • Support for higher education under the post-9/11 GI Bill.
    • Navy College Program to support education while on service.
  • Life Insurance: Servicemembers’ Group Life Insurance (SGLI) provides coverage up to $500,000.
  • Vacation: ten or more federal holidays plus thirty days of paid vacation each year.
  • Extra Benefits:
    • Exchanges and commissaries provide tax-free purchasing.
    • Discounted travel via military resorts, access to fitness centers, and leisure amenities.
Navy-MMA-Rating-Machinists-Mates-Non-Nuclear-Submarine-Auxiliary-Image-704X396

Training and Career Opportunities

Boot Camp & Technical Training

  • Recruit Training Command Great Lakes (Boot Camp).
  • Basic Enlisted Submarine School – Groton, CT (9 weeks).
    • Learn basic submarine systems, operations, and safety.

Specialized MMA Training

  • Machinist’s Mate “A” School – Groton, CT (9 weeks).
    • Covers mechanical theory, safety, piping systems, valves, pumps, tools, and watchstanding.
    • Hands-on training in mechanical systems and maintenance procedures.
  • Machinist’s Mate “C” School – Groton, CT, King’s Bay, GA, or Bangor, WA (7 weeks).
    • Advanced technical training for auxiliary systems operators.
    • Focuses on detailed equipment maintenance, troubleshooting, and operational procedures.

First Assignments

  • MMAs typically serve on submarines but may also be assigned to naval repair stations in the U.S. or overseas.
  • Shore duty may include instructor roles, recruiting duty, or intermediate maintenance activities (SIMAs).

Advanced Training & Career Progression

Post-Service Opportunities

  • Civilian careers in power plant operations, industrial machinery, mechanical systems maintenance, and engineering support.
  • Directly transferable skills to high-demand industries.

Career Balance

  • MMAs spend about 70% of their time at sea and 30% on shore duty.
  • Submarine pay ranges from $75 to $600 per month, depending on experience and rank.

Qualifications to Join

Basic Requirements

  • Must be a U.S. citizen and eligible for a security clearance.
  • High school diploma or GED required.
  • Must volunteer for submarine duty.

ASVAB Score Requirements

  • VE + AR + MK + EI = 207 or
  • AR + GS + MC + EI = 207

Skills & Personal Traits

  • Strong math skills – Needed for calculations and technical work.
  • Good speaking ability – Clear communication is key in tight spaces.
  • Attention to detail – Record-keeping and system monitoring require precision.
  • Mechanical aptitude – Must be comfortable working with tools, machinery, and complex mechanical systems.
  • Good manual dexterity – Many repairs require fine motor skills.
  • Physical stamina – The job can be physically demanding, hot, noisy, and repetitive.
  • Team playerYou work in close quarters—getting along is non-negotiable.

The enlistment qualification requirements above are current as of Fiscal Year 2025, per the Navy Personnel Command. This information is not readily available to the public.

So, contact your local Navy Enlisted Recruiter for the most current requirements to join the Navy as an enlisted Sailor.

More Information

If you wish to learn more about becoming a Machinist’s Mate Auxiliary (MMA), contact your local Navy Enlisted Recruiter. They will provide you with more detailed information you’re unlikely to find online.

You may also be interested in the following related Navy Enlisted jobs:

Ted Kingston
I’m a Navy veteran who used to serve as a Navy recruiter. This website is the most reliable source of information for all Enlisted Navy Sailor aspirants. In coordination with a network of current and former Navy recruiters, my goal is to make reliable information easily available to you so you can make informed career decisions.

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