Twin Disc MG5091 Marine Transmission Parts Catalog

Introduction: Smooth, Reliable Power for Marine Applications

The Twin Disc MG5091 marine transmission is trusted by vessel operators for its robust design, smooth power transfer, and long-lasting performance . Built for a variety of marine applications—including fishing boats, workboats, offshore supply vessels, and recreational yachts —the MG5091 is engineered to meet the rigorous demands of marine propulsion systems.

At Diesel Pro Power , we offer a complete range of MG5091 parts to keep your transmission operating at peak efficiency. Whether you need parts for routine maintenance, a major overhaul, or a complete rebuild, we’ve got you covered with fast shipping and expert support.

Rebuilt Twin Disc MG5091 Marine Transmissions: Gear Ratios and Applications

At Diesel Pro Power, we offer a range of rebuilt Twin Disc MG5091 marine transmissions , each meticulously remanufactured to meet OEM specifications. These transmissions are available in various gear ratios to suit different vessel requirements:

Twin Disc MG5091 Marine Transmission 1.5:1 – Rebuilt for Sale

Ideal for high-speed vessels such as patrol boats and fast ferries, the 1.5:1 ratio provides a balance between speed and torque. This configuration is suitable for applications where rapid acceleration and higher cruising speeds are essential.

Twin Disc MG5091 Marine Transmission 1.7:1 – Rebuilt for Sale

The 1.7:1 ratio offers a versatile balance between speed and power, making it suitable for a variety of vessels, including commercial fishing boats and recreational crafts. This ratio ensures efficient fuel consumption while maintaining adequate thrust.

Twin Disc MG5091 Marine Transmission 2.0:1 – Rebuilt for Sale

Designed for vessels requiring more torque, the 2.0:1 ratio is commonly used in workboats and utility vessels. This configuration provides enhanced pulling power, making it ideal for towing and heavy-duty operations.

Twin Disc MG5091 Marine Transmission 2.5:1 – Rebuilt for Sale

The 2.5:1 ratio is tailored for heavy-duty applications where maximum torque is necessary. This setup is often found in tugboats and larger fishing vessels, ensuring reliable performance under substantial loads.

Twin Disc MG5091 Marine Transmission 3.0:1 – Rebuilt for Sale

Offering a balance between speed and torque, the 3.0:1 ratio is suitable for vessels that require moderate thrust and speed, such as mid-sized commercial boats.

Twin Disc MG5091 Marine Transmission 3.5:1 – Rebuilt for Sale

The 3.5:1 ratio provides increased torque for heavier vessels, such as cargo boats and larger fishing vessels. This configuration ensures reliable performance under substantial loads.

Twin Disc MG5091 Marine Transmission 4.0:1 – Rebuilt for Sale

Engineered for applications needing high thrust at lower speeds, including trawlers and utility boats, the 4.0:1 ratio offers enhanced durability and torque capacity.

Twin Disc MG5091 Marine Transmission 4.5:1 – Rebuilt for Sale

Provides substantial torque and excellent control for heavy-duty commercial vessels. The 4.5:1 ratio ensures reliable performance under high-load conditions, making it a preferred choice for demanding operations.

Twin Disc MG5091 Marine Transmission 5.0:1 – Rebuilt for Sale

Delivers maximum torque and control for the most challenging applications, including tugboats and heavy-duty commercial vessels. The 5.0:1 ratio supports continuous heavy-load performance and long-term durability.

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Each rebuilt transmission includes essential components such as the mechanical selector valve assembly, pilot housing flange, oil pump, oil level gauge, and output flange. Please note that the drive ring is sold separately.

By selecting the appropriate gear ratio for your vessel's specific needs, you can optimize performance, fuel efficiency, and operational reliability.

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Essential MG5091 Parts for Maintenance and Overhaul

Overhaul Plate Kit – For Twin Disc MG5091 Transmission

Our overhaul plate kit includes all brass friction plates and steel plates necessary for a full clutch rebuild. Engineered for durability, this kit restores smooth clutch engagement and prolongs the life of your transmission.

Gasket Set – For Twin Disc MG5091 Transmission

Includes main housing gaskets, O-rings, seal rings, and auxiliary gaskets to ensure a leak-free seal during overhauls or maintenance, preventing fluid leaks and maintaining performance.

Bearing Kit – For Twin Disc MG5091 Transmission

The bearing kit features precision-engineered bearings designed to reduce friction, support shaft alignment, and ensure quiet, efficient operation.

Ring Kit – For Twin Disc MG5091 Transmission

Essential for restoring system tolerances and preventing leaks, our ring kit includes sealing and retaining rings for a complete rebuild.

Plate – For Twin Disc MG5091 Transmission

Individual brass friction plates and steel plates are available for targeted repairs, maintaining clutch performance without needing a full kit.

Rubber Block (Coupling) – For Twin Disc MG5091 Transmission

The rubber block absorbs vibrations and compensates for shaft misalignments, reducing stress on the drivetrain and improving comfort and longevity.

Seal – For Twin Disc MG5091 Transmission

High-quality input and output shaft seals ensure internal pressure and fluid integrity, preventing contamination and wear on internal components.

Oil Pump & Filter – For Twin Disc MG5091 Transmission

Keeps oil circulating and clean, protecting gears, bearings, and other components from damage and wear.

Gauges – For Twin Disc MG5091 Transmission

Accurately monitor oil pressure, temperature, and other system parameters, helping operators detect issues early and maintain peak performance.

Oil Cooler – For Twin Disc MG5091 Transmission

Regulates transmission temperature to prevent overheating and prolong component life. Built from corrosion-resistant materials for reliable marine performance.

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Marine Transmission Specifications & Applications of the Twin Disc MG5091

Overview of the Twin Disc MG5091 Marine Transmission

The Twin Disc MG5091 is a robust marine transmission engineered for continuous-duty commercial vessels that require reliable high-horsepower performance. Built on the legacy of the MG509 series, the MG5091 incorporates upgraded torque handling, improved cooling capacity, and flexible configuration options. It is ideal for fishing trawlers, supply boats, utility vessels, and pushboats that demand uninterrupted operation and maximum uptime.

Featuring a heavy-duty cast-iron housing, oil-cooled multi-disc hydraulic clutch, and multiple reduction ratios, the MG5091 is designed to perform in some of the most demanding marine environments. This transmission is well-suited for mid- to large-displacement diesel engines in the 400–600 horsepower range and is available with either straight or down-angle output configurations to match vessel layout requirements.

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Key Specifications of the Twin Disc MG5091

• Type: Marine transmission, hydraulically actuated

• Horsepower Rating (Approximate):

• Continuous Duty: Up to 450 HP @ 1800 RPM

• Intermittent Duty: Up to 550 HP @ 2300 RPM

• Maximum Input Speed: 2500 RPM

• Reduction Ratios Available:

• 1.47:1

• 1.93:1

• 2.50:1

• 2.95:1

• 3.00:1

• 3.50:1

• Input Housing: SAE No. 1 or SAE No. 2

• Flywheel Compatibility: 14", 11.5" (depending on engine model)

• Clutch Type: Oil-cooled multi-disc hydraulic clutch

• Cooling System: Standard oil-to-water heat exchanger; oil-to-air optional

• Lubrication: Internal pressure-fed oil pump with full-flow system

• Oil Capacity: Approximately 10–12 quarts depending on configuration

• Dry Weight: Approx. 525–625 lbs

• Mounting Options: Straight or down-angle output

• Rotation Compatibility: Accepts both clockwise and counterclockwise engine rotation

• Optional Features:

• Mechanical or hydraulic PTO

• Trolling valve for slow-speed maneuvering

• Rigid or flex mounts

• Companion flange or custom output shafts

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Common Marine Applications for the MG5091

The MG5091 is ideal for mid-sized commercial vessels that require consistent propulsion and gear performance under variable load conditions. This transmission is built for continuous duty and is frequently found in:

• Commercial Fishing Trawlers: Designed to handle the heavy loads and long shifts of commercial offshore fishing.

• Pushboats and Towboats: Supports high-torque diesel engines with reliable clutch performance for harbor and river operations.

• Utility and Supply Boats: Dependable in dynamic positioning, standby, and support vessel roles.

• Ferries and Transport Craft: Smooth operation for vessels with demanding service schedules and tight docking needs.

• Dredging and Survey Boats: Reliable under frequent gear changes and power-on-load operation.

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Most Common Engine Models Paired with the Twin Disc MG5091

The MG5091 is most often paired with six-cylinder and V8 marine diesel engines in the 400–600 horsepower range. These engines are commonly used in commercial fleets that prioritize longevity, torque output, and aftermarket support.

Cummins Marine Engines

• Cummins QSM11

• Cummins N14 Marine

• Cummins KTA19 (light commercial ratings)
  These engines provide reliable torque and smooth operation under high-load scenarios, making them ideal for pairing with the MG5091.

Detroit Diesel Marine Engines

• Detroit Diesel 8V92TI

• Detroit Diesel 12V71
  Trusted in repowers and legacy installations, these two-stroke Detroit engines match well with the MG5091’s torque capacity and clutch engagement design.

Caterpillar Marine Engines

• Caterpillar 3406C / 3406E

• Caterpillar 3408C

• Caterpillar 3412 (light-duty ratings)
  These high-output Caterpillar engines are commonly used in workboats and utility vessels operating in continuous-duty environments.

John Deere Marine Engines

• John Deere 6135SFM85

• John Deere 6090AFM85
  With high torque output and SAE housing compatibility, these engines pair well with MG5091 transmissions in dredging, fishing, and service vessels.

MTU & MAN Marine Engines

• Medium-duty MTU and MAN engines (especially older V6 and V8 configurations) are found in international commercial applications with MG5091 transmissions due to the gearbox’s flexibility and aftermarket availability.

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Advantages of the Twin Disc MG5091

• Heavy-Duty Geartrain: Built to handle frequent operation under load with minimal wear and extended service intervals.

• Hydraulic Clutch System: Oil-cooled multi-disc clutch ensures smooth shifting even during extended operation.

• Multiple Gear Ratios: Ideal for customizing vessel performance based on hull design and mission profile.

• Straight or Down-Angle Configurations: Offers layout flexibility for engine room design and shaft alignment.

• Dependable Performance: Proven in fleets operating 24/7 in demanding commercial conditions.

• Strong Aftermarket Support: Diesel Pro Power carries parts and kits for full rebuild or regular maintenance.

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Ideal Use Cases for the MG5091

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Additional Resources

Practical Guide Outline for Twin Disc MG-5091 Marine Gear

Introduction for Twin Disc MG-5091 Marine Gear

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• Overview of Twin Disc MG-5091 Marine Transmission

• Importance of preventive maintenance and proper repair practices

• Use of premium aftermarket parts to reduce downtime

• Disclaimer: Refer to OEM service manual (SM-259) for full technical specs
  

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Specifications and Identification for Twin Disc MG-5091 Marine Gear

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Gearbox Specifications for Twin Disc MG-5091 Marine Gear

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• Weight

• Dimensions

• Gear Ratios

• Input Power Rating

• Rotation Direction
  

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Serial Number Identification for Twin Disc MG-5091 Marine Gear

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• Where to locate it

• How to interpret it
  

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Safety Guidelines for Twin Disc MG-5091 Marine Gear

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Personal Protective Equipment (PPE) for Twin Disc MG-5091 Marine Gear

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• Gloves, goggles, and protective clothing

• Safe lifting techniques
  

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Safe Maintenance Practices for Twin Disc MG-5091 Marine Gear

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• Lockout/tagout procedure

• Proper ventilation and workspace cleanliness
  

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Installation Procedures for Twin Disc MG-5091 Marine Gear

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Pre-Installation Inspection for Twin Disc MG-5091 Marine Gear

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• Mounting flange condition

• Alignment checks

• Shaft runout inspection
  

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Alignment and Mounting for Twin Disc MG-5091 Marine Gear

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• Soft foot correction

• Coupling alignment methods

• Bolt torque specifications
  

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Operating Instructions for Twin Disc MG-5091 Marine Gear

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Startup Checklist for Twin Disc MG-5091 Marine Gear

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• Oil level check

• Filter inspection

• Monitoring gauges
  

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Operating Parameters for Twin Disc MG-5091 Marine Gear

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• Normal operating temperature

• Oil pressure ranges

• Noise and vibration limits
  

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Lubrication and Fluid Guidelines for Twin Disc MG-5091 Marine Gear

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Approved Oil Types for Twin Disc MG-5091 Marine Gear

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• Viscosity requirements

• Compatible brands
  

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Oil Change Intervals for Twin Disc MG-5091 Marine Gear

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• Initial break-in period

• Regular change schedule
  

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Oil Filter Maintenance for Twin Disc MG-5091 Marine Gear

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• Filter replacement process

• Inspection tips
  

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Routine Maintenance Schedule for Twin Disc MG-5091 Marine Gear

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Daily Checks for Twin Disc MG-5091 Marine Gear

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• Oil level

• Visual inspections
  

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Weekly Tasks for Twin Disc MG-5091 Marine Gear

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• Leak checks

• Coupling checks
  

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Monthly/Quarterly Tasks for Twin Disc MG-5091 Marine Gear

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• Alignment re-checks

• Oil sample analysis
  

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Troubleshooting Guide for Twin Disc MG-5091 Marine Gear

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Common Symptoms and Probable Causes for Twin Disc MG-5091 Marine Gear

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• Gear slippage

• Overheating

• Abnormal noise

• Loss of oil pressure
  

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Diagnostic Tips for Twin Disc MG-5091 Marine Gear

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• Tools required

• How to isolate issues
  

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Disassembly and Inspection for Twin Disc MG-5091 Marine Gear

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Tools Required for Twin Disc MG-5091 Marine Gear

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• Pullers, dial indicators, torque wrenches
  

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Disassembly Tips for Twin Disc MG-5091 Marine Gear

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• Draining fluid

• Gear housing removal

• Input/output shaft removal
  

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Inspection Points for Twin Disc MG-5091 Marine Gear

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• Wear patterns

• Backlash measurement

• Shaft endplay
  

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Reassembly Procedures for Twin Disc MG-5091 Marine Gear

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Cleaning and Preparation for Twin Disc MG-5091 Marine Gear

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• Parts washing

• Inspection before reuse
  

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Gasket and Seal Installation for Twin Disc MG-5091 Marine Gear

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• Recommended sealants

• Pre-lube techniques
  

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Final Assembly and Testing for Twin Disc MG-5091 Marine Gear

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• Bolt torques

• Function tests
  

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Parts Replacement Guide for Twin Disc MG-5091 Marine Gear

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Commonly Replaced Components for Twin Disc MG-5091 Marine Gear

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• Clutch plates

• Bearings

• Gaskets and seals
  

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Rebuild Kit Options for Twin Disc MG-5091 Marine Gear

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• What’s included in the kit

• Using Diesel Pro Power aftermarket kits
  

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Technical Torque Specs and Tolerances for Twin Disc MG-5091 Marine Gear

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Torque Settings for Twin Disc MG-5091 Marine Gear

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• Flange bolts

• Cover bolts

• Shaft nuts
  

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Tolerances for Twin Disc MG-5091 Marine Gear

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• Shaft runout

• Gear backlash

• Endplay
  

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Storage and Preservation for Twin Disc MG-5091 Marine Gear

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Long-Term Storage for Twin Disc MG-5091 Marine Gear

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• Draining procedures

• Rust inhibitors
  

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Seasonal Layup for Twin Disc MG-5091 Marine Gear

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• Recommended checks before restarting
  

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50 Frequently Asked Questions (FAQ) for Twin Disc MG-5091 Marine Gear

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Frequently Asked Questions (FAQs) about the Twin Disc MG5091

1. What vessels commonly use the Twin Disc MG5091?

The MG5091 is used in commercial fishing boats, offshore supply vessels, trawlers, workboats, and recreational yachts , offering smooth, reliable power transfer.

2. What essential parts should I keep on hand for my MG5091?

Key components include the overhaul plate kit, gasket set, bearing kit, ring kit, plate, coupling, seal, oil pump & filter, gauges, and oil cooler .

3. What’s included in the overhaul plate kit?

It contains all brass friction plates and steel plates needed for a complete clutch rebuild, ensuring smooth engagement and extended service life.

4. How do I know when to replace the rubber block?

Replace it if you notice increased vibrations, unusual noises, or visible signs of wear or cracking during inspections.

5. How often should I change the oil and filter in the MG5091?

Change the oil and filter every 500 hours of operation or annually , whichever comes first, to maintain optimal performance and reduce wear.

6. What type of oil is recommended for the MG5091?

Use SAE 30W engine oil for temperatures between 150°F and 185°F, and SAE 40W oil for 185°F to 210°F.

7. Are Diesel Pro’s aftermarket parts reliable for the MG5091?

Yes! Our aftermarket parts are designed to meet or exceed OEM standards , providing long-lasting performance at a competitive price.

8. How fast can I get MG5091 parts from Diesel Pro Power?

Orders are typically processed within 24 hours , with fast worldwide shipping to minimize downtime.

9. What signs indicate my MG5091 needs maintenance or overhaul?

Look for slipping gears, fluid leaks, increased vibrations, unusual noises, overheating, or decreased performance .

10. Can Diesel Pro Power help me select the right parts for my MG5091?

Absolutely! Our team offers expert technical support, part selection assistance, and installation guidance for all your MG5091 needs.