MMA

Machinist's Mate Auxiliary

Machinist''s Mate Auxiliary (MMA) is the submarine non-nuclear mechanical specialty. MMAs own everything aft of the reactor compartment that isn''t primary propulsion: high-pressure air, hydraulics, atmosphere control (CO2 scrubbers, O2 generators, H2 burners), the trim and drain systems, ship''s service turbine generators'' auxiliaries, weapons-handling hydraulics, the outboard plant, and the atmosphere-analysis equipment that keeps the crew alive on long submerged runs.

MMA is a non-nuclear submarine rating distinct from MMN (Machinist''s Mate Nuclear), which runs the primary plant. MMA sailors are the boat''s mechanical generalists — they diagnose and repair across dozens of auxiliary systems and stand watch as Auxiliaryman of the Watch (A-Gang), Chief of the Watch, and Diving Officer of the Watch.

The pipeline runs from Basic Enlisted Submarine School in Groton into MMA ''A'' School, also at Naval Submarine Base New London. Work is physically demanding, hot, and tight-quartered. Civilian translation is strongest toward industrial mechanic, HVAC-R, and maritime engineering trades.

Overall

4.8/10

Burnout5.1

Lifestyle3.0

Civilian ROI

Quick Stats

Enlistment BonusNo active bonus

Civilian Sector Transferability$65k–$110k

Advancement OutlookAverage

Manning %92%

Initial Contract3 yr active /

Medical Requirements

✓Vision: Corrects to 20/20
✓Normal color perception
✓Normal hearing
✓No speech impediment

Security Clearance

Secret~$3K–$15K civilian sector value

Requires a National Agency Check with Local Agency Check and Credit Check (NACLC). Processing typically takes 1–3 months and is initiated early in your training pipeline.

ASVAB Requirements

AFQT Minimum

Who This Is Best For

Best for hands-on mechanical candidates who want submarine duty without the nuclear pipeline, and who are looking toward industrial-mechanic, HVAC-R, or maritime trade careers afterward.

+Pros

✓Strong civilian career transition

–Cons

✗Significant sea duty

Real Opinions

+Positive

✓

“I kept the air clean. If you want to live under the water in a steel tube that's closed on both ends for months at a time, you need people like me.”

The Lean Submariner|

✓

“Proudest work of my life with some of the best men I have ever known.”

The Lean Submariner|

–Negative & Mixed

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Recruiter vs Reality

What the recruiter says vs. what it's actually like.

🫡 Recruiter says

“A-Gang keeps the sub habitable — you'll be the hero of the boat.”

💀 Reality

Source: https://theleansubmariner.com/2019/06/07/it-wasnt-for-the-glory-life-as-a-submarine-auxiliaryman/

MMAs run oxygen generators, CO2 scrubbers, hydraulics, HP air, diesel, and sanitary systems. Retired A-Ganger: "We were in charge of the shit tanks too. If you really want to see grown men cry, shut down those babies for a few hours."

🫡 Recruiter says

“Great for a mechanical civilian career — HVAC, refrigeration, diesel.”

💀 Reality

Source: https://www.cool.osd.mil/usn/moc/index.html?moc=mma

The Navy-to-civilian translation is real, but MMA systems are sub-specific (EAB, CAMS, O2 gens). Generic HVAC/refrigeration employers may not recognize Navy training without extra certs. Civilian diesel/marine-mechanic certs are the most direct path.

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Advancement Outlook

E-2 to E-4 Advancement Outlook

Time to E-4: 30 months total

E-1 → E-2: 9 months at E-1. Automatic
E-2 → E-3: 9 months at E-2. Automatic
E-3 → E-4: 12 months at E-3. Automatic

E-4 is automatic — competitive advancement starts at E-5

How to advance faster to E-4

Your recruiter can process you in at E-2 or E-3 on day one if you qualify. Every rung skipped shortens the path to E-4 by months. Official transcripts / certificates required at enlistment.

E-2 →Easy
2 years of JROTC completed. Easiest common path if your high school offers JROTC.
E-2 →Moderate
24+ semester hours/ 36+ quarter hours of college credit (below the associate's threshold). Roughly one full year of college.
E-2 →Moderate
Civil Air Patrol Billy Mitchell Award. Achievable with consistent cadet participation, but requires testing and leadership time.
E-2 →Moderate
Sea Cadet Corps — reaching the Sea Cadet E-2 rate (join by age 17).
E-2 to E-3 →Moderate
Boot camp leadership roles — roles don't auto-pin rank. Advancement comes from earning Honor Recruit or Hall of Fame at graduation (one award only, not stacked).
- Honor Recruit up to E-2 — effectively the #1 ranked recruit in your division (~60-80 recruits), one Sailor per division per cycle. Selection is based on cumulative performance across all three academic exams, Physical Readiness Test (PRT) scores, uniform and personnel inspections, military bearing, and peer/Recruit Division Commander (RDC) evaluations. Roles that typically compete at this level:
  - Assistant LPO (ALPO) — deputy to the LPO.
  - Master-at-Arms (MAA) — barracks cleanliness, standards, and discipline.
  - Yeoman (YN) — division admin, paperwork, and tracking.
  - Educational Petty Officer (EPO) — study groups, test prep, and academic remediation.
  - Religious Petty Officer (RPO) — coordinates chapel and religious services.
  - Athletic Petty Officer (APO) — leads PT and fitness assessments.
  - Mail Petty Officer — handles mail distribution and tracking.
  - Section Leaders — squad-level leaders below the division-wide roles.
- Hall of Fame up to E-3 — the most elite recognition at Recruit Training Command (RTC), awarded Navy-wide rather than per division. Requires exceptional performance in every training metric: top-tier scores on all three academic exams (typically 90%+), "Outstanding" on the final Physical Readiness Test (PRT), near-perfect uniform and personnel inspections, held a division leadership role with strong performance, and zero remediation, infractions, or negative marks across the full training cycle. Senior leadership roles positioned to compete:
E-3 →Moderate
3 years of JROTC completed (any service branch). Straightforward if your high school has the program — three school years of enrollment.
E-3 →Hard
Eagle Scout (BSA) or Gold Award (GSUSA) — the highest youth scouting awards. Typically takes years of participation and a capstone service project.
E-3 →Hard
Associate's degree (or 48+ semester hours / 72+ quarter hours of college credit, 100-level or higher from an accredited institution). Two years of full-time college.
E-3 →Hard
Civil Air Patrol Earhart Award. Uncommon — only a small fraction of CAP cadets reach this level.
E-3 →Hard
Sea Cadet Corps — reaching the Sea Cadet E-3 rate (join by age 16).

Ceiling is E-3 at accession — stacking qualifications doesn't push you to E-4 out of the gate.

Ways to accelerate E-4 after you're in

Very HardMeritorious Advancement Program (MAP) — Command-nominated promotion that skips the exam entirely. Each command gets a small seasonal quota of MAP slots and hands them to the top performers based on evaluation ranking. Fastest path on paper, but you're competing directly with every other sailor at your command.

Rules can change — verify current criteria with your recruiter and in the latest Navy Recruiting Manual (COMNAVCRUITCOM) before signing any paperwork that assumes a specific entry paygrade.

E-5 and E-6 Advancement Outlook

Average★☆★☆

1 of 4 factors working in your favor · 1 working against you

▼
Manning
E5 85%E6 100%
E5 is balanced while E6 is overmanned. Your advancement outlook depends on which paygrade you're promoting into next.
Source: N12 Enlisted Community Status Brief, 1 Apr 26
●
Enlistment bonus
No
No active enlistment bonus for this rate. Most ratings do not offer one in any given fiscal year, so this is a neutral signal on its own.
▲
Overall Selective Reenlistment Bonus (SRB) Outlook
Competitive SRB added/increased · SRB reduced/eliminated
Navy is paying a substantial bonus to retain sailors. Strong signal that billets are staying empty at senior paygrades.

Bonuses — Click here to see your military pay

Initial Enlistment Bonus

No active bonus for this rate

You May Qualify for a Navy Enlisted Classification (NEC)

Specialties within this rate you can select, some with additional compensation. Each NEC has its own training, bonus potential, and career path.

0000Any NEC or no NEC (all qualifying Sailors in this rating)

Selective Reenlistment Bonus (SRB)

🟡

First Reenlistment (17 mo to 6 yrs Active Duty)

$45,000

Max

Reduced · effective 2025-12-18

🟢

Second Reenlistment (6 to 10 yrs Active Duty)

$60,000

Max

Active (unchanged)

🟢

Third Reenlistment (10 to 14 yrs Active Duty)

$30,000

Max

Active (unchanged)

Q10BMachinist's Mate Auxiliary (MMA) Leading Chief Petty Officer (LCPO)

Manages and supervises personnel and programs associated with Auxiliary Division. Supervises maintenance scheduling, management and utilization of maintenance scheduling software; develops Auxiliary Division training plans, using the school house to train Sailors; coordinates and communicates with IMA/PMT, fleet Diesel Engine Inspector (DEI) and other outside agencies.

Requirements

Member must have a Secret Security Clearance.
Member must be a U.S. citizen.

Q33BSSN 774 Diesel Engine (Caterpiller) Maintenance Technician

Perform preventive, organizational and/or intermediate level maintenance on SSN 774 Caterpillar diesel engines and components including pumps, blowers, governors, injectors, cylinders, liners, pistons, connection rods, bearings, crankshaft, vertical drive assembly, lubrication oil, fuel oil, scavenging air, exhaust, starting air and cooling water systems.

Requirements

Member must possess a Secret Security clearance.

Q34ASSN 774 Class Advanced Auxiliary Equipment Technician

Operates and performs organizational level maintenance on all assigned auxiliary equipment.

Requirements

Member must possess a Secret Security Clearance.

Q53ALow Pressure Electrolyzer (LPE) Operator

Operates and performs required mechanical maintenance on the Low Pressure Electrolyzer on board submarines.

Requirements

Must be qualified in submarines; qualified O2 Clean Worker and have completed course 652-0085.

700JLanding Craft Air Cushion (LCAC) Propulsion and Auxiliary Systems Maintenance Technician

Performs Organizational and Intermediate Level Maintenance on LCAC-100 Propulsion and Auxiliary Systems.

Requirements

Member must complete the LCAC-100 Maintainer Differences Trainer.
Member must submit NAVPERS 1221/6 with Commanding Officer's endorsement to BUPERS 312 for awarding of this NEC code.

730BLCAC Mechanical Systems Maintenance Technician

Performs organizational and intermediate level maintenance on LCAC propulsion and lift systems.

735BAutomated Electrolytic Oxygen Generator (AEOG) Mechanical Maintenance Technician

Operates and performs Mechanical Maintenance on the AEOG on board submarines.

Requirements

Must be qualified in submarines and complete DODUSNSLCSOBT 03173.

739BSSN/SSBN Diesel Engine (Fairbanks-Morse) Maintenance Technician

Performs preventive, organizational and/or intermediate level maintenance on submarine diesel engines and components including pumps, blowers, governors, injectors, cylinders, liners, pistons, connection rods, bearings, crankshaft, vertical drive assembly, lubrication oil, fuel oil, scavenging air, exhaust, starting air, and cooling water systems.

Requirements

Must be a qualified diesel operator with 1 year operating experience.

740BElectrolytic Oxygen Generator (Model 6L16) Operator/Mechanical Maintainer

Operates, troubleshoots, and performs basic corrective maintenance on the Model 6L16 Electrolytic Oxygen Generator.

Requirements

Must be qualified in submarines.

741BHigh and Low Pressure Cryogenic Technician

Operates, tests, inspects, and performs organizational and intermediate level maintenance on high and low pressure liquid oxygen and nitrogen generating plants. Tests liquid oxygen and liquid nitrogen for purity and acetylene contamination. Performs required checks on O2N2 compressed gas cylinders prior to and after charging them to the proper pressure.

Requirements

Type II or Universal certification in accordance with EPA mandate is required.
Member must have completed a minimum of twenty-four (24) months of shipboard experience working on and maintaining 02 N2 Plant and the Commanding Officer's recommendation in order to attend the prerequisite formal training.

742BRefrigeration and Air Conditioning Systems Technician

Starts, operates, performs organizational and/or intermediate level maintenance and overhauls all types of refrigeration, cooling and air conditioning equipment utilizing centrifugal or reciprocating compressors, including accessories and controls. Identifies abnormal conditions and corrects malfunctions that may lead to inadequate refrigeration, cooling or air conditioning.

747BDiesel Engine Inspector

Inspects and assesses material condition, monitors general readiness, provides on-board maintenance training, and diagnoses improper operating procedures and equipment casualties/failures and supports corrective actions of marine main propulsion diesel engines, diesel generators, and component systems.

Requirements

Personnel must have 5 years of experience in operation and maintenance of main propulsion diesel engines prior to attending A-652-0311.
Upon final certification, NAVSEA 05 DEI Program Manager will submit NAVPERS 1221/6 with supporting documentation to BUPERS-312 for award of this NEC code.
Attendance of A-652-0320, Diesel Engine C School Core is a prerequisite to attending A-652-0311.
After completion of A-652-0311, Sailors will be ordered to a maximum 30 day I-Stop at either Southwest Regional Maintenance Center (SWRMC) San Diego, CA (UIC 55236) or Mid-Atlantic Regional Maintenance Center (MARMC) Norfolk, VA (UIC 50094) for final certification.
For Sailors who earn the NEC code as E6, award of the NEC code will be held in abeyance until frocked to E7.

747CDiesel Engine Inspector (DEI) Candidate

Identifies potential DEI candidates who have been interviewed and endorsed by certified diesel engine inspectors.

Requirements

Member must be able to work in tight quarters and often confined locations, i.e. engine enclosures, inside engine sump, etc.
Normal hearing (defines threshold levels must be greater than 30db and less than 45db without aid), normal/corrected eye sight of 20/20.
Member must be able to read and properly interpret tech manuals, drawings and other repair maintenance procedures.
Member must be able to properly explain and use maintenance and engine specific special tooling for routine and corrective maintenance/repair of diesel engines.
Member must be able to obtain/hold a secret security clearance.
Source Rating MMA candidates must also be screened for submarine service.
Member must complete milestones in accordance with the EN and MMA Career Path Milestones.
Member must submit command endorsed NAVPERS 1221/6 to BUPERS-312 to be awarded this NEC code.

752BElectrolytic Oxygen Generator (Model 6L16) Electrical Technician

Performs organizational and intermediate level maintenance on electrical components of the 6L16 Oxygen Generator.

Requirements

To attend the course and receive this NEC code, MMA personnel must be qualified as a 6L16 EOG inspector at a submarine squadron, staff or IMA, and have at least 2 years of 6L16 EOG operating experience.

756ABarber

Provides haircuts that conform to Navy grooming standards; maintains barber equipment; meets sanitation requirements.

Requirements

EMN, ETN and MMN source rating personnel must be submarine designated.

761CNavy Afloat Maintenance Training Strategy (NAMTS) Submarine Auxiliaryman Valve Repair Technician

Performs NAMTS operational and intermediate level maintenance procedures in inspecting, troubleshooting, repairing, maintaining and testing submarine valve systems and components. Demonstrates knowledge of operational and intermediate level repair procedures, repair and maintenance standards, quality assurance specifications and proper use of industrial machinery.

Requirements

Member must provide documented completion of tasks for this skill to be awarded this NEC code; demonstration of advanced-level proficiency during hands-on training; and production work as specified in the current JQR located at https://navsea.navy.deps.mil/field/CNRMC/NAMTS/jqrs.aspx. Training is led by journeyman-level craftsmen and supplemented by appropriate self- paced instruction consistent with Department of Labor journeyman certification.

761DNavy Afloat Maintenance Training Strategy (NAMTS) Submarine Auxiliaryman Pump Repair Technician

Performs Navy Afloat Maintenance Training Strategy (NAMTS) operational and intermediate level maintenance procedures in inspecting, troubleshooting, repairing, maintaining and testing submarine pump systems and components.

Requirements

Member must provide documented completion of tasks for this skill to be awarded this NEC code; demonstration of advanced-level proficiency during hands-on training; and production work as specified in the current JQR located at https://navsea.navy.deps.mil/field/CNRMC/NAMTS/jqrs.aspx. Training is led by journeyman-level craftsmen and supplemented by appropriate self- paced instruction consistent with Department of Labor journeyman certification.

768AOil Analysis Operator/Evaluator

Performs analysis and evaluation of oils/lubricants. Uses spectrometric analysis to evaluate oil/lubricants for wear metals. Uses physical property tests to evaluate oil/lubricants for properties such as viscosity, particulate presents, water, or other chemical presents and flash point. Maintains records of analytical data. Performs trend analysis.

774CSubmarine Disqualification Tracker

Member has been disqualified from serving on submarine duty and is still in the process of converting to another Source Rating. Once the conversion process is complete, this NEC code shall be achieved.

785ASDV MK8/MK11 Team Technician

Performs maintenance and support of classified combatant submersible systems and related equipment assigned to Naval Special Warfare (NSW) SEAL Delivery Vehicle (SDV) Teams. Major equipment includes MK8 and MK11 SDVs, Dry Deck Shelters (DDS), Transport Systems, and accessory equipment.

Requirements

Course K-431-0306 is for ETV and ITE, ITN, ITR ratings.
NEC code will be awarded upon completion of formal training program conducted at the Naval Special Warfare Center and recommendation of the Commanding Officer that certifies member as a qualified SDV MK8 and MK11 Team Technician.
The Naval Reserve indicator is "R" for ETV, ITE, ITN, ITR personnel.

786AAdvance SEAL Delivery System Maintainer

Perform organizational and intermediate level maintenance training on the ASDS. Possesses the unique skills required to conduct preventive and corrective maintenance on hull, mechanical, electronic and electronic and electrical systems on this new acquisition combatant submersible.

Requirements

Formal training and PQS is required to receive this NEC code.
Personnel will normally be qualified in submarines.

789AUnmanned Undersea Vehicle (UUV) Operator

Performs duties as a member, or in support of a UUV activity, to include sortie planning, launch and recovery, local or remote watch, post mission analysis, and organizational level maintenance.

Requirements

To be eligible for this NEC Code member must have: a. Qualified on a Navy UUV system. b. Completed at least two weeks of formal classroom instruction on the operation and maintenance of UUVs (e.g., factory schooling, university short-course, MK-18 operator course, etc.). c. Completed twelve months of OJT and primary duties involved UUV operations.
Reserve Force members may satisfy the OJT requirement by 100 days of Annual Training (AT) and Active Duty for Training (ADT) or 18 months of Individual Duty for Training (IDT) and AT in support of UUV operations.
Submit NAVPERS 1221/6 to BUPERS-312 with endorsement from UUV activity. 277

797BNavy Afloat Maintenance Training Strategy (NAMTS) Submarine Auxiliaryman Refrigeration Repair Technician

Performs NAMTS operational and intermediate level maintenance procedures in inspecting, troubleshooting, repairing, maintaining and testing submarine compressors, heat exchangers and refrigeration systems as well as recharging systems and aligning equipment shafts.

Requirements

Awarding of this NEC code is based on documented completion of tasks for this skill; demonstration of advanced-level proficiency during hands- on training; and production work as specified in the current JQR located at https://navsea.navy.deps.mil/field/CNRMC/NAMTS/jqrs.aspx. Training is led by journeyman-level craftsmen and supplemented by appropriate self-paced instruction consistent with Department of Labor journeyman certification.

797CNavy Afloat Maintenance Training Strategy (NAMTS) Submarine Auxiliaryman Hydraulics Repair Technician

Performs NAMTS operational and intermediate level maintenance procedures in inspecting, troubleshooting, repairing, maintaining and testing submarine hydraulics systems and components. Demonstrates knowledge of operational and intermediate level repair procedures, repair and maintenance standards, quality assurance specifications and proper use of industrial machinery.

Requirements

Awarding of this NEC code is based on documented completion of tasks for this skill; demonstration of advanced-level proficiency during hands- on training; and production work as specified in the current JQR located at https://navsea.navy.deps.mil/field/CNRMC/NAMTS/jqrs.aspx. Training is led by journeyman-level craftsmen and supplemented by appropriate self-paced instruction consistent with Department of Labor journeyman certification.

Machinist's Mate Auxiliary

Quick Stats

Security Clearance

ASVAB Requirements

Who This Is Best For

+Pros

–Cons

Real Opinions

+Positive

–Negative & Mixed

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Recruiter vs Reality

Horror Stories

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Medical Requirements — detail

Remarks

Training Pipeline — Total ~32 weeks (7 months)

Calculate Your End Training Date and Holidays and Events You Will Miss During Training

Career Progression Milestones

Advancement Outlook

Bonuses — Click here to see your military pay

You May Qualify for a Navy Enlisted Classification (NEC)

Potential Civilian Post-Navy Outcomes

Post-Navy Salary Trajectory

Free Certifications & Credentials

Retention & Burnout

Lifestyle3/10

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