The IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer is a high‑capacity, towable mortar mixer engineered for professional masons, stucco crews, and contractors who need to mix large volumes of mortar, stucco, and grout quickly and consistently. With a 12 cubic foot batch output, aggressive horizontal paddles, and powerful Honda gas or 240V electric motor options, it is the largest model in IMER’s HSM horizontal shaft mixer line.

Overview of the IMER HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer

The HSM 12 is a 12 cu ft towable horizontal shaft mortar mixer designed and engineered to be one of the best mortar mixers on the market. It uses a horizontal shaft with paddles inside a stationary steel drum, rather than a rotating barrel, to mix mortars, stuccos, and grouts with more power and less noise.

This towable mixer is part of the IMER HSM 6, 8 & 12 family and is built specifically for high‑production crews who need big batches without sacrificing mix quality. Thanks to its gearbox design, the HSM 12 quietly transmits more engine power directly to the mixing paddles, producing a strong, thorough blend every time.

Key Specifications: IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer

The HSM 12 combines a large drum, heavy‑duty frame, and high‑output motor/engine options.

Capacity and dimensions

From IMER’s HSM product sheet and distributor specs:

• Batch output (cubic feet): 12 cu ft

• Bag capacity: 3.5 – 4 bags (standard premix 80 lb equivalents)

• Drum: 12 cu ft heavy‑duty steel drum

• Overall height: 56.5 in

• Overall width: 52.5 in (HSM 12 is wider than HSM 6 & 8)

• Charging height: 58 in

• Length (with tow bar): 84 in (104.5 in with tow bar extended)

• Tires: B78 x 13 in highway‑rated tires

• Weight: 1,200 lbs

• Highway towable: Yes

This makes the IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer a true high‑capacity machine capable of producing large mortar and stucco batches for demanding projects.

Gas and Electric Power Options

Like the other HSM mixers, the HSM 12 is available in both gas and electric versions to match different jobsite requirements.

From IMER’s official HSM 6, 8 & 12 spec sheet:

• Gas model (HSM 12 gas):

  • Engine: Honda GX390, 13 HP (some retailers list 11.7 HP GX390)

  • Ideal for outdoor jobs and sites without reliable power.

• Electric model (HSM 12 electric):

  • Motor: 240V, 5 HP industrial electric motor.

  • Suitable for large indoor projects and emissions‑sensitive environments where 240V power is available.

Typical model numbers include 1130121 for the gas steel drum version and 1130122 for the electric steel drum version, listed by IMER parts and distributors.

The gearbox design efficiently transfers power from either the Honda engine or electric motor to the mixing paddles, providing strong torque for heavy mixes while keeping noise levels under about 79 dB.

Horizontal Shaft Mixing System and Drum Design

The defining feature of the IMER HSM 12 is its horizontal shaft mixing system inside a stationary steel drum.

Key mixing design elements:

• Horizontal shaft with aggressive paddles that sweep through the entire drum, ensuring fast and complete mixing of mortar and stucco.

• Enclosed gearbox that transmits more engine power to the paddles, improving blending efficiency while staying extra quiet.

• Optional spiral mixing blades available that IMER notes can make mixing up to 30% faster on HSM models.

This system delivers a very consistent mix, which is critical for masonry mortar, stucco coats, and grout where workability and uniform texture matter. The heavy‑gauge steel drum is designed for long‑term durability in harsh jobsite conditions.

Towable Chassis, Hitch, and Mobility

The HSM 12 is built on a rugged towable chassis that allows it to be moved between jobs like a small trailer.

Tow and mobility features include:

• 2 inch ball hitch as standard, with optional pintle loop available upon request.

• Highway‑rated B78 x 13 in tires capable of safe towing at road speeds.

• Heavy‑duty steel frame with forklift pockets on some HSM models, allowing easy loading and positioning in yards or on large sites.

Because the IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer is highway towable, crews can move it from jobsite to jobsite quickly without a dedicated flatbed, which is especially beneficial for masonry and stucco contractors working multiple projects.

Mixing Performance, Bag Capacity, and Output

The HSM 12 is designed for high‑output mortar production.

From IMER and dealer specifications:

• Batch output: 12 cu ft per load.

• Bag capacity: Approximately 3.5–4 bags per batch (standard 80 lb preblended mortar or stucco).

This allows crews to mix large batches capable of supplying multiple masons or stucco applicators continuously. The powerful Honda GX390 or 5 HP electric motor ensures the mixer can handle dense mortar and stucco mixes without bogging down.

The enclosed gearbox also reduces heat and gear wear, meaning the machine maintains performance over longer runs and extends component life.

Typical Applications for the HSM 12

The IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer is built for serious professional use on jobs where large quantities of mortar or stucco are required. Common applications include:

• Large masonry projects:

  • Mixing mortar for CMU block walls, structural brick, and large stone veneer installations.

• Stucco and plaster work:

  • Producing base and finish coats for multi‑story residential, commercial, or institutional buildings.

• Grout and structural fills:

  • Preparing grout for block cell fills, cores, and repair work requiring high output.

• High‑volume restoration or façade work where consistent batches are needed all day.

Its 12 cu ft batch size and robust drive system make the HSM 12 ideal for crews that would outgrow a 6 or 8 cu ft mixer but still want towable mobility and efficient horizontal shaft mixing.

Features That Improve Jobsite Efficiency and Safety

IMER designed the HSM 12 to improve productivity and operator safety on demanding jobsites.

Notable features from the HSM product sheet include:

• Quiet enclosed gearbox that produces less noise and heat, improving working conditions and reducing wear.

• Large grab handle and locking dump handle that make dumping the load easy, safe, and controlled.

• Extra‑large safety grate over the drum opening to prevent accidental contact and control debris, supplied as standard.

• Pillow block bearings mounted externally to keep the shaft spinning smoothly and simplify maintenance.

• Optional torsion bar axle available for improved towing and ride quality upon request.

These features help crews mix and discharge material more safely and efficiently, lowering fatigue and improving output per man‑hour.

Maintenance, Durability, and IMER Support

The HSM 12 is built as a contractor‑duty machine with long‑term durability in mind. Its heavy steel drum, robust frame, and industrial‑grade gearbox are designed for daily use on busy projects.

Routine maintenance typically includes:

• Cleaning the drum and paddles thoroughly after each use to prevent hardened material buildup.

• Checking the gearbox and shaft bearings according to IMER’s maintenance schedule.

• Inspecting and maintaining the Honda GX390 engine (oil, air filter, spark plug) on gas models.

• Verifying electrical connections and motor condition on 240V electric models.

• Checking tire pressure, hitch connections, and safety chains before towing.

IMER USA provides product pages and a combined HSM 6, 8 & 12 product sheet, while distributors offer spec sheets, parts, and service for both gas and electric HSM 12 models.

Why Choose the IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer?

The IMER – HSM 12 – 12 cu ft Horizontal Shaft Mortar Mixer is an excellent choice for contractors who need a large‑capacity, towable mortar mixer that delivers quiet, powerful mixing day after day. Its 12 cu ft batch output, 3.5–4 bag capacity, aggressive horizontal paddles, and choice of Honda GX390 gas engine or 5 HP 240V electric motor make it ideal for big masonry, stucco, and grout jobs.

With a rugged towable frame, highway‑rated tires, safety grate, quiet gearbox, and optional upgraded mixing blades, the HSM 12 stands out as a professional‑grade solution for contractors who demand high production, consistent mix quality, and long‑term durability from their mortar mixer.