Twin Disc MG520 Marine Transmission Parts Catalog

Introduction: Dependable Power and Durability for Marine Applications

The Twin Disc MG520 marine transmission is a trusted and proven solution for marine operators who require reliability, performance, and longevity. Whether powering commercial fishing boats, workboats, offshore vessels, or recreational craft, the MG520’s robust construction and precision engineering deliver smooth power transfer, operational efficiency, and consistent performance in demanding environments.

At Diesel Pro Power, we are committed to offering a complete range of MG520 parts, including rebuilt transmissions, overhaul plate kits, gasket sets, plate kits, rubber blocks, and oil pump and filter assemblies. With our 24-hour worldwide shipping, competitive pricing, and expert customer support, you can count on us to keep your MG520 transmission operating at its best.

Rebuilt Twin Disc MG520 Marine Transmissions for Sale

Our rebuilt MG520 transmissions are meticulously reconditioned to meet OEM specifications, ensuring reliable operation and extended service life. Each transmission undergoes complete disassembly, comprehensive inspection, replacement of worn components, reassembly with premium materials, and thorough testing under load conditions.

Every rebuilt MG520 transmission comes equipped with:

• Mechanical selector valve assembly (control valve) for precise and smooth gear changes.

• Pilot housing flange for secure and stable engine connection.

• Oil pump to maintain constant lubrication, reducing wear on internal parts.

• Oil level gauge for easy fluid monitoring and maintenance.

• Output flange ensuring efficient and durable power transfer to the propeller shaft.

Note: Drive ring is sold separately. All rebuilt MG520 transmissions are sold with a refundable core deposit. See details for more information.

Available Gear Ratios:

• Twin Disc MG520 Marine Transmission 4.5:1 for Sale
  Delivers excellent torque and control for demanding commercial marine operations, including towing, dredging, and heavy cargo transport. This ratio ensures strong, reliable propulsion for vessels operating in high-load conditions.

• Twin Disc MG520 Marine Transmission 5.0:1 for Sale
  Provides maximum torque and thrust for heavy-duty marine applications, including large workboats and tugboats. The 5.0:1 ratio is engineered for continuous operation under demanding loads, ensuring dependable performance and vessel control.

• Twin Disc MG520 Marine Transmission 6.0:1 for Sale
  Offers exceptional torque and control, making it perfect for tugboats, trawlers, and offshore support vessels. The 6.0:1 ratio delivers superior pulling power, ensuring smooth propulsion even in challenging marine environments.

• Twin Disc MG520 Marine Transmission 7.0:1 for Sale
  Designed for vessels that require extremely high thrust and low-speed control, such as heavy-duty towing and deep-sea operations. The 7.0:1 ratio ensures outstanding torque output and precise maneuverability under extreme conditions.

• Twin Disc MG520 Marine Transmission 7.5:1 for Sale
  The highest available ratio for the MG520, offering maximum torque and control for the most demanding marine operations. Ideal for large, heavily loaded vessels, the 7.5:1 ratio provides exceptional pulling power and stability in rough seas.

Each rebuilt MG520 transmission is available in stock and ready for fast delivery, ensuring minimal downtime for your vessel.

Our Selection of Twin Disc MG520 Parts

As the largest online retailer specializing in Twin Disc marine engine parts, Diesel Pro Power ensures fast, reliable access to the essential parts you need. Let’s explore the high-quality components available for the MG520:

Overhaul Plate Kit – For Twin Disc MG520 Transmission

Our overhaul plate kit includes all the necessary brass friction plates and steel plates for a complete clutch rebuild. Designed to restore smooth clutch engagement and consistent transmission performance, these kits are essential for major overhauls and preventive maintenance. Made from high-strength materials, the plates are built to withstand high-load operations and prolonged use.

Gasket Set – For Twin Disc MG520 Transmission

Our complete gasket set includes main housing gaskets, O-rings, seal rings, and auxiliary gaskets that ensure a leak-free seal and maintain system pressure during maintenance or overhaul. Engineered from premium materials resistant to oil, saltwater, and extreme temperatures, these gaskets protect against contamination and ensure optimal transmission performance over time.

Plate Kit – For Twin Disc MG520 Transmission

Our plate kit offers a selection of individual brass and steel plates for targeted clutch system repairs. Ideal for addressing specific wear or damage, these high-quality plates are precision-crafted for durability and consistent engagement. A cost-effective solution for restoring performance without the need for a full overhaul kit.

Rubber Blocks (Couplings) – For Twin Disc MG520 Transmission

The rubber block, also known as a torsional isolator, connects the transmission output flange to the propeller shaft. It effectively absorbs torsional vibrations, reduces stress on drivetrain components, and compensates for misalignments caused by hull flex or engine movement. Crafted from high-quality marine-grade materials, the coupling ensures quiet operation, enhanced comfort, and extended system lifespan.

Oil Pump and Filter – For Twin Disc MG520 Transmission

Our oil pump and filter assembly is critical for maintaining consistent lubrication and system cleanliness, reducing wear on internal components and extending transmission life. The oil pump ensures continuous oil flow under demanding conditions, while the high-efficiency filter removes contaminants and debris for optimal performance.

Why Choose Diesel Pro Power for MG520 Parts?

• 24-Hour Worldwide Shipping: We process and ship orders within 24 hours, ensuring rapid delivery and minimal downtime.

• Extensive Inventory: Our comprehensive selection of MG520 parts, including hard-to-find components, ensures you get exactly what you need.

• Expert Customer Support: Our team offers personalized assistance with product selection, technical advice, and troubleshooting.

• Over 15,000 Satisfied Customers: Trusted globally by marine professionals and private boat owners for reliable service and high-quality parts.

• Easy-to-Use Online Platform: Browse, select, and order parts for your MG520 transmission quickly and conveniently.

Frequently Asked Questions (FAQs) about the Twin Disc MG520

1. What types of vessels use the MG520 transmission?

The MG520 is used in a wide range of vessels, including fishing boats, tugboats, offshore supply vessels, workboats, and recreational yachts.

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

Key components include the rebuilt gear, overhaul plate kit, gasket set, plate kit, rubber blocks, and oil pump and filter.

3. What is included in the overhaul plate kit?

The kit contains all brass friction plates and steel plates needed for a full clutch rebuild, ensuring smooth and reliable clutch engagement.

4. How often should I replace the oil and filter?

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

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

Replace the coupling if you notice increased vibrations, unusual noises, or visible wear and cracks during inspections.

6. Are Diesel Pro’s aftermarket parts reliable?

Yes! All our parts meet or exceed OEM standards, providing long-lasting performance and durability.

7. How quickly can I get MG520 parts?

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

8. What are signs that my MG520 transmission needs service?

Look for fluid leaks, slipping gears, overheating, unusual noises, or reduced performance.

9. Can Diesel Pro Power help me select the right parts?

Absolutely! Our experienced team offers expert technical support and guidance to ensure proper part selection and installation.

10. Do you offer warranties on rebuilt transmissions and parts?

Yes, we provide a comprehensive warranty on rebuilt transmissions and parts. Contact us for specific details.

Order Twin Disc MG520 Parts Today

At Diesel Pro Power, we make it easy to find and order the Twin Disc MG520 marine transmission parts you need. With fast shipping, expert support, and a commitment to quality, we’re the trusted choice for marine operators worldwide.

Browse our selection today and place your order with confidence. For assistance, contact us at 888-433-4735 (US) or 305-545-5588 (International) during business hours (8 a.m. to 5 p.m. EST, Monday–Friday).

Marine Transmission Specifications & Applications of the Twin Disc MG520

Overview of the Twin Disc MG520 Marine Transmission

The Twin Disc MG520 is a heavy-duty marine transmission engineered to handle high torque loads in continuous-duty and high-horsepower commercial marine applications. Designed for vessels operating in demanding offshore and industrial environments, the MG520 offers superior strength, robust gear ratios, and long-term reliability for operators who depend on uninterrupted propulsion.

Built for marine diesel engines producing up to 1,200 horsepower, the MG520 supports multiple mounting configurations, a wide selection of gear reductions, and optional power take-off (PTO) and trolling valve setups. It is frequently found in tugboats, offshore supply vessels, trawlers, and workboats that require consistent performance over extended service hours.

Key Specifications of the Twin Disc MG520

• Type: Heavy-duty marine transmission with hydraulic clutch

• Horsepower Rating (Approximate):

• Continuous Duty: Up to 1,000 HP @ 1800 RPM

• Intermittent Duty: Up to 1,200 HP @ 2300 RPM

• Maximum Input Speed: 2500 RPM

• Reduction Ratios Available:

• 2.00:1

• 2.50:1

• 3.00:1

• 3.50:1

• 4.00:1

• 4.50:1

• Input Housing: SAE No. 0 or SAE No. 1

• Flywheel Compatibility: 18", 14"

• Clutch Type: Oil-cooled, hydraulically actuated multi-disc clutch

• Cooling System: Oil-to-water heat exchanger standard; oil-to-air option available

• Lubrication System: Pressure lubrication via internal oil pump

• Oil Capacity: Approximately 24–30 quarts depending on configuration

• Dry Weight: Approximately 1,500–1,800 lbs

• Mounting Options: Straight or down-angle configurations

• Rotation Compatibility: Bi-directional input for LH or RH rotating engines

• Optional Features:

• Hydraulic or mechanical PTO

• Trolling valve for low-speed control

• Custom shaft or flange output configurations

Common Marine Applications for the MG520

Designed to thrive in high-load environments, the MG520 is commonly installed in the following marine applications:

• Harbor and Ocean-Going Tugboats: Provides rugged, high-torque propulsion needed for towing and pushboat operations.

• Offshore Supply Vessels (OSVs): Ensures reliable service for cargo, personnel, and fuel transport across offshore sectors.

• Heavy Commercial Fishing Vessels: Ideal for deep-sea trawlers requiring consistent torque and resistance to gear fatigue.

• Dredging Equipment and Support Vessels: Interfaces seamlessly with hydraulic systems and pumps via PTO.

• Research, Cable-Laying, and Utility Ships: Robust, low-maintenance choice for 24/7 operation in complex mission profiles.

Most Common Engine Models Paired with the Twin Disc MG520

The MG520 is typically paired with high-output marine diesel engines in the 800–1,200 HP range. Its strong housing and high gear ratio capacity make it compatible with many large-displacement commercial engines.

Cummins Marine Engines

• Cummins KTA38-M

• Cummins QSK38 (select commercial ratings)
  Used extensively in pushboats and offshore service vessels, these Cummins engines pair well with the MG520’s rugged clutch and gear assembly.

Caterpillar Marine Engines

• Caterpillar 3412E

• Caterpillar C32 ACERT (commercial ratings)
  Commonly deployed in OSVs and industrial fishing vessels, these engines offer torque profiles that match the MG520’s capabilities.

Detroit Diesel Marine Engines

• Detroit Diesel 16V92TI

• Detroit Diesel 16V149
  Legacy engines still in operation in tug fleets and industrial marine applications often rely on MG520 or MG514 series transmissions.

MTU Marine Engines

• MTU Series 4000 (low-output ratings)
  Used in high-performance and large-scale vessels, MTU engines work well with MG520 units when outfitted with appropriate ratio and housing options.

Advantages of the Twin Disc MG520

• Extreme Torque Handling: One of Twin Disc’s most robust transmissions for vessels with high bollard pull or load demands.

• Reliable Hydraulic Clutch System: Multi-disc oil-cooled clutch provides longevity in full-load marine operation.

• Wide Ratio Availability: Gear reductions from 2:1 to 4.5:1 enable precise tuning for propeller pitch and vessel speed requirements.

• Support for High-Capacity PTOs: Interfaces easily with hydraulic pumps or onboard systems through optional PTO.

• Engineered for Continuous Duty: Built for uninterrupted use in harsh marine conditions with extended oil change intervals.

Ideal Use Cases for the MG520