Navy Machinist’s Mate (MM): Definitive Guide (2025)

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

Navy ships go far. Across oceans, to every continent. Missions don’t happen without power. That’s where Machinist’s Mates (MMs) come in.

You’ll repair steam turbines, maintain propulsion, adjust aircraft elevators—keep the ship running. Systems break. MMs fix them. Engines, pumps, hydraulics, air conditioning—if it moves, it’s your job.

Work takes you all over the ship. Cruisers, destroyers—every system, hands-on. Learn it, fix it, keep things moving. No ship reaches its mission without MMs doing their job first.

If you’re interested, let’s go.

Job Description

navy-mm-insignia
MM Insignia – Credit: U.S. Navy

Machinist’s Mates keep the Navy ship’s mechanical systems running, from propulsion and power generation to auxiliary equipment. They work with everything from steering engines and pumps to refrigeration, elevators, and laundry equipment.

They also operate and maintain boilers, heat exchangers, and turbo generators, ensuring ships have the power to complete their missions. MMs handle fuel, lubricating oils, and industrial gases, keeping systems running smoothly.

Where They Work

MMs serve in fire rooms, boiler rooms, engine rooms, and maintenance shops. These spaces can be hot, loud, and physically demanding, requiring teamwork and hands-on problem-solving.

With about 6,300 Sailors in the MM rating, they are found on traditional steam-powered ships and at land-based stations.

Specific Responsibilities

  • Align piping systems for oil, water, air, and steam.
  • Operate ship boilers and steam turbines for propulsion.
  • Run turbo generators for electrical power.
  • Clean, adjust, test, and maintain boilers, engines, and generators.
  • Maintain auxiliary machinerysteering engines, pumps, valves, winches, and elevators.
  • Operate and service water desalination plants.
  • Maintain galley equipment and air conditioning systems.
  • Repair valves, compressors, turbines, and hydraulic systems.
  • Generate and review machinery reports and records.

If it powers, moves, cools, or pumps, MMs keep it working. Ships don’t run without them.

Over a 20-year Navy career, MMs typically spend:

  • 70% of their time at sea with fleet units.
  • 30% on shore duty at naval repair facilities or training commands.

Shore Assignments May Include:

  • Shore Intermediate Maintenance Activities (SIMAs) – Repair and upkeep of fleet equipment.
  • Instructors at Class “A” or “C” Schools – Training new MMs.
  • Recruit Company Commanders – Leading and training new recruits.
  • Navy Recruiting Duty – Helping bring in the next generation of Sailors.

MMs spend most of their careers in fleet operations, but shore assignments provide opportunities for mentorship, leadership, and technical training.

Fun fact: Did you know they’re nicknamed ‘Snipes‘? Here’s Why…

Different Roles

Steam-powered ships don’t move without trained specialists. They operate turbines, fix pumps, keep systems working. Everything from powering the ship to running A/C and refrigeration.

MMs have three roles—each with more responsibility.


Steam Plant Auxiliary Systems Maintainer (Learning the Job)

  • Works on steam turbines, reduction gears, pumps, oil purifiers.
  • Handles steering engines, elevators, refrigeration, A/C, desalination.
  • Aligns piping for oil, water, air, and steam.
  • Runs boilers and steam turbines for propulsion.
  • Cleans, adjusts, tests, and repairs equipment.
  • Learns under supervision.

Steam Plant Auxiliary Systems Technician (More Experience, More Responsibility)

  • Operates and maintains propulsion turbines, generators, and auxiliary machinery.
  • Works with compressed gas plants, hydraulic systems, winches, and valves.
  • Controls boilers, steam turbines, and turbo-generators.
  • Runs preventive maintenance on main engines and support systems.
  • Repairs compressors, turbines, and control devices.
  • Works more independently, mentors Maintainers.

Steam Plant Auxiliary Systems Manager (The Expert, The Leader)

  • Knows every system, from propulsion to auxiliary equipment.
  • Runs boilers, power systems, and mechanical operations.
  • Leads repairs on pumps, turbines, refrigeration, steering engines.
  • Trains and supervises Technicians and Maintainers.
  • Analyzes reports, troubleshoots systems, makes improvements.

Maintainers learn. Technicians take charge. Managers lead. If it powers, cools, or moves the ship, they make sure it works.

Navy-MM-Rating-Machinists-Mate-Image-704X396

Rank Structure

Pay GradeRateAbbreviationTitle
E-1Fireman RecruitFRFireman Recruit
E-2Fireman ApprenticeFAFireman Apprentice
E-3FiremanFNFireman
E-4Machinist’s Mate Third ClassMM3Petty Officer Third Class
E-5Machinist’s Mate Second ClassMM2Petty Officer Second Class
E-6Machinist’s Mate First ClassMM1Petty Officer First Class
E-7Chief Machinist’s MateMMCChief Petty Officer
E-8Senior Chief Machinist’s MateMMCSSenior Chief Petty Officer
E-9Master Chief Machinist’s MateMMCMMaster 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:

PaygradeLess 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.

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.

Training and Career Opportunities

After Boot Camp at Recruit Training Command Great Lakes, Machinist’s Mates begin specialized training in mechanical systems, maintenance, and ship operations.

Initial Training

Basic Engineering Common Core & “A” School – Great Lakes, IL (9 weeks)

  • Mechanical theory, tools, and safety.
  • Piping systems, valves, pumps, and gears.
  • Lubrication systems, bearings, couplings.
  • Technical documentation & Maintenance Material Management System (3M).
  • Basic watch standing procedures.
  • Hands-on training in classrooms and shops.

After training, MMs are assigned to ships, shore stations, or naval repair activities in the U.S. or overseas.

Advanced Training & Career Growth

  • Additional technical training available later in career.
  • Promotion opportunities are competitive and based on performance.
  • Sailors with leadership aspirations and a college degree may pursue Officer roles.

Post-Service Opportunities

MM training directly translates to civilian jobs in:

  • Industrial machinery maintenance
  • Power plant operations
  • Engineering and mechanical systems

Whether maintaining Navy propulsion systems or civilian power plants, the skills learned as an MM open doors after service.

Qualifications to Join

Basic Requirements

To become a Machinist’s Mate (MM) in the Navy, you must meet the following requirements:

  • High school diploma or equivalent required.
  • Must be a U.S. citizen and eligible for security clearance.
  • Good speaking skills and ability to work as part of a team.
  • Aptitude for tools and mechanical devices.
  • Manual dexterity and physical stamina—the job is hands-on and physically demanding.
  • Resourcefulness and interest in learning new mechanical systems.
  • Normal hearing required (strict standards apply).

ASVAB Requirements (Waivers considered case-by-case)

  • VE + AR + MK + AS = 195 OR
  • VE + AR + MK + AO = 200

Hearing Standards (Must meet all conditions to qualify)

  • Frequencies Tested: 3000Hz, 4000Hz, 5000Hz, 6000Hz
  • Average threshold level across all four frequencies must be less than 30dB.
  • No single frequency can exceed 45dB.
  • If hearing exceeds these limits, the applicant is ineligible for MM.

MMs need mechanical ability, stamina, teamwork, and good hearing. If you like hands-on work, problem-solving, and keeping ships running, this job is for you.

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 (MM), 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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