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The Twin Disc MG-502 marine transmission is an exceptional choice for pleasure craft, sportfishing boats, and small commercial vessels. Renowned for its reliability, smooth operation, and compact size, the MG-502 is engineered to deliver consistent power and performance in light to medium-duty marine applications. With over 40,000+ satisfied customers, Diesel Pro Power offers a comprehensive selection of MG-502 parts to keep your vessel running strong. Type: Marine Transmission Power Rating: Suitable for light and medium-duty applications Typical Applications: Pleasure yachts and sportfishing boats Charter boats and harbor taxis Small passenger ferries and tour boats Dive boats, patrol boats, and pilot boats Features: Compact design, smooth engagement, fuel-efficient operation, low maintenance A rebuilt MG-502 transmission offers a highly cost-effective solution to extend the operational life of your vessel, especially when compared to the cost of purchasing a brand-new transmission. Diesel Pro Power’s rebuilt units are meticulously reconditioned to meet and even exceed original equipment manufacturer (OEM) standards. Each unit undergoes comprehensive inspection, cleaning, and reassembly to ensure optimal performance and longevity. Our rebuilt transmissions are not only restored to like-new condition, but are also tested under real-world conditions to verify their performance. From the replacement of worn components to the recalibration of critical systems, every rebuilt MG-502 is designed to provide the reliability and smooth operation that marine professionals demand. Our rebuilt MG-502 transmissions come in the following gear ratios, each optimized for different marine applications, offering flexibility to match your specific vessel’s engine nd usage profile: Rebuilt Twin Disc MG502 Gear (1.54:1 Ratio): This gear ratio is perfect for vessels that require a balance of speed and moderate torque. It’s ideally suited for sportfishing boats, high-performance pleasure craft, and vessels where acceleration and cruising efficiency are equally important. The 1.54:1 ratio enables vessels to achieve quick planing speeds, while still providing enough thrust for responsive handling in various conditions. Rebuilt Twin Disc MG502 Gear (2.00:1 Ratio): A versatile choice for vessels that need a higher thrust-to-speed balance. The 2.00:1 ratio is commonly used in heavier recreational vessels, charter boats, and harbor ferries that require more torque for maneuvering and maintaining stability under load. It provides a noticeable increase in propeller thrust, improving the vessel’s ability to handle varying sea conditions and passenger capacities. Rebuilt Twin Disc MG502 Gear (2.47:1 Ratio): This gear ratio is tailored for applications that require maximum low-speed thrust, such as dive boats, tour vessels, and other operations where precise, slow-speed control is essential. The 2.47:1 ratio delivers exceptional pulling power, ideal for maintaining stability in strong currents or when navigating tight docking spaces. It’s perfect for operations that prioritize safety, reliability, and precise handling over high speed. Precision Engineering: Every rebuilt MG-502 transmission is crafted to OEM specifications, with a focus on quality assurance at every stage of the rebuild process. Components are inspected, reconditioned, or replaced as necessary to ensure the final product performs as well as or better than new. Custom Fit for Your Vessel: With multiple gear ratios available, you can select the ideal configuration that matches your vessel’s engine performance, operational needs, and cruising conditions. This ensures maximum efficiency, reliability, and responsiveness on the water. Warranty Protection: Diesel Pro Power stands behind every rebuilt MG-502 transmission with a limited warranty, offering you peace of mind and assurance of product quality and reliability. Our commitment to excellence means you can count on your transmission for years of dependable service. Budget-Friendly Solution: A rebuilt transmission provides a cost-effective alternative to purchasing a new unit, allowing vessel owners to maximize their investment while maintaining top-tier performance. Whether for a pleasure craft, charter boat, or light commercial vessel, a rebuilt MG-502 from Diesel Pro Power delivers significant savings without compromising on quality. Fast Availability and Expert Support: Diesel Pro Power maintains a comprehensive inventory of rebuilt MG-502 units, ensuring fast order fulfillment and delivery. Our knowledgeable team can help you select the right gear ratio and provide technical support throughout the installation and maintenance process. Our plate kits include friction plates, steel plates, seals, and rings—everything you need for a smooth rebuild. Designed for marine use, ensuring reliable performance and long service life. Maintains smooth clutch engagement, reducing wear on transmission components. A complete gasket set ensures that your MG-502 stays sealed and leak-free after maintenance. Includes main housing gaskets, O-rings, seal rings, and auxiliary gaskets. Prevents leaks and withstands the harsh marine environment. Essential for smooth operation and longevity: Input shaft bearings for handling engine torque. Output shaft bearings for supporting propeller load. Thrust bearings for maintaining axial alignment. Reduces friction and noise, extending the life of your transmission. The oil pump is the heart of lubrication for the MG-502, ensuring continuous oil flow and cooling. Maintains optimal pressure, even under demanding conditions. Prevents oil starvation and keeps your transmission components well-lubricated. Rubber blocks, also known as torsional isolators or flexible couplings, are critical components that connect the transmission output flange to the propeller shaft. These blocks absorb torsional vibrations and misalignments, protecting both the transmission and downstream components from stress and potential damage. Vibration Dampening: Rubber blocks effectively isolate the transmission from torsional vibrations generated by the engine and propeller, reducing noise and wear. Compensation for Misalignment: Flexible design accommodates slight misalignments between transmission and shaft, which is common in marine environments due to hull flexing and engine movement. Extended Component Life: By reducing shock loads and vibrations, rubber blocks help extend the lifespan of critical transmission and drivetrain parts. Marine-Grade Durability: Constructed from high-quality materials resistant to oil, saltwater, and extreme temperatures, ensuring long-term reliability in marine conditions. Easy Replacement: Designed for straightforward installation and replacement during transmission servicing or overhauls. The Twin Disc MG502 is a compact, lightweight, and reliable marine transmission designed for light- to medium-duty commercial and recreational vessels. Known for its mechanical simplicity and durable design, it is a preferred choice for operators who require consistent performance and easy maintenance in tight engine compartments. As a mechanical (non-electronic) marine gearbox, the MG502 features either an aluminum alloy or cast iron housing depending on the application. With both straight and down-angle output options available, this gearbox offers installation flexibility to accommodate various engine-room layouts. It is especially popular in workboats, patrol craft, fishing vessels, and utility boats due to its dependable operation and service-friendly design. Type: Marine mechanical transmission Maximum Input Power: 120 to 160 horsepower at 2500 RPM (depending on gear ratio) Maximum Input Speed: 2500 RPM Reduction Ratios Available: 1.50:1 2.00:1 2.47:1 2.95:1 Rotation Options: Supports both left-hand and right-hand engine rotation Input Housing: SAE No. 3 or No. 4 flywheel housing Mounting: Engine-mounted Clutch Type: Mechanically actuated hydraulic multi-disc clutch Lubrication: Internal lubrication system with dedicated oil pump Recommended Oil: SAE 30 non-detergent or ATF (check specifications per model year) Oil Capacity: Approximately 2.5 to 3.5 quarts Dry Weight: Approximately 135 to 165 lbs depending on configuration Cooling Options: Oil cooler (optional, application dependent) The Twin Disc MG502 is a dependable solution for small to mid-size marine vessels where mechanical simplicity, compact size, and ease of service are critical. Common marine applications include: Fishing Vessels: Widely used in crab boats, lobster boats, and coastal fishing vessels where torque delivery and low maintenance are essential. Patrol Boats: Popular in law enforcement, harbor patrol, and military small craft where reliability is paramount. Tour Boats and Passenger Ferries: Smooth engagement and durable construction make it suitable for small ferry boats and charter vessels. Private Yachts and Cruising Sailboats: Often found in auxiliary engine systems, especially where space is limited. Workboats and Utility Vessels: Used in barges, tug tenders, and supply boats operating in harbor and inland waters. The MG502 is typically paired with marine diesel engines in the 120 to 160 horsepower range. It integrates well with many engine brands that use SAE No. 3 or No. 4 housings. Below are the most common engine models found alongside the MG502 in marine installations: Cummins 4BT (Marine Version) Cummins 6BT / 6BTA 5.9 Cummins QSB 5.9 These engines are known for their fuel efficiency, high torque output, and proven marine track record. The MG502 offers a solid match for these engines in fishing vessels and patrol craft. Detroit Diesel 3-53 Detroit Diesel 4-53 Detroit Diesel 6V53 (light-duty marine ratings only) These two- and four-cycle Detroit engines are frequently used in older commercial vessels, and the MG502 remains a popular replacement transmission for repower and rebuild projects involving these platforms. Perkins 4.236 Perkins 6.354 The MG502 is often paired with Perkins engines in sailboat auxiliary power and small commercial vessels, especially in international fleets where Perkins engines are prevalent. Caterpillar 3054 Caterpillar 3116 (light-duty only) Caterpillar’s smaller marine diesels match well with the MG502 where engine bay space is restricted and mechanical simplicity is preferred. Yanmar 4LH Series Yanmar engines are favored in many light-duty commercial and private vessels. The MG502’s mechanical actuation pairs well with Yanmar's robust inline diesels. Volvo TAMD41 Older Volvo marine diesels such as the TAMD41 have frequently been retrofitted with Twin Disc transmissions, especially in refit projects where an original gearbox failed or parts are no longer available. Proper alignment and matching torque curves between engine and transmission are critical. Diesel Pro Power can assist in confirming compatibility and recommending the correct MG502 configuration for your engine setup. Compact & Lightweight: Ideal for tight engine rooms and vessels with strict weight constraints. Mechanical Design: No electronic components to fail; easier to troubleshoot and repair in the field. Available Gear Ratios: Several reduction options to optimize vessel speed and thrust based on hull and propeller characteristics. Flexible Engine Pairing: Compatible with a broad range of marine diesel engines. Global Support: Diesel Pro Power offers aftermarket parts for the MG502 with fast delivery and expert support. Vessel Type MG502 Suitability Comments Coastal Fishing Boats Excellent Reliable, low-maintenance, compatible with common engine models Harbor Patrol Boats Excellent Quick shift response, proven durability Recreational Cruisers Excellent Compact and quiet with appropriate gearing Ocean-Going Trawlers Not Recommended MG502 not designed for continuous heavy-duty applications Sailboat Auxiliaries Excellent Especially for auxiliary diesel engine configurations Practical Guide To Servicing Your Twin Disc MG502 Overview of the Twin Disc MG502 Marine Gear Importance of Regular Maintenance Safety Precautions 1. Understanding the Twin Disc MG502 Marine Gear Basic Components and Their Functions Operational Principles Common Applications Required Tools and Equipment Safety Gear and Precautions Inspection Steps Before Service Maintenance Schedule Overview Preparation for Disassembly Step-by-Step Disassembly Process Identifying Wear and Tear Components Handling and Storing Components Visual Inspection Techniques Identifying Common Faults (e.g., Leaks, Cracks, Wear) Diagnostic Procedures for Malfunctions Measuring Tolerances and Clearances 5. Cleaning and Maintenance Procedures Cleaning Guidelines for Major Components Lubrication Requirements Seal and Gasket Replacement Best Practices for Preventing Corrosion Pre-Assembly Checklist Step-by-Step Reassembly Guide Torque Specifications for Fasteners Testing Component Alignment 7. Final Testing and Operational Checks Initial Testing Procedures Load Testing and Calibration Noise and Vibration Checks Post-Service Inspection Checklist 8. Troubleshooting Common Issues Difficulty Engaging Gear Excessive Noise or Vibration Fluid Leaks and Seal Failures Overheating Concerns Control System Malfunctions Daily, Weekly, and Monthly Maintenance Tasks Seasonal Checks for Marine Environments Component Life Expectancy and Replacement Guidelines 10. Recommended Spare Parts and Tools Essential Spare Parts List Recommended Tools for Onboard Repairs Tips for Efficient Parts Replacement 11. Safety and Compliance Considerations Environmental Regulations for Marine Equipment Waste Disposal and Recycling of Old Parts Best Practices for Safe Operation 12. Storage and Preservation Tips Long-Term Storage Preparations Preventive Measures Against Environmental Damage Periodic Checks During Storage Frequently Asked Questions (FAQ) About The Twin Disc MG502 (Marine Gear) Disclaimer: For more technical and detailed instructions, refer to the OEM service manual provided by Twin Disc Incorporated. This guide is intended for general maintenance assistance and does not replace official service protocols. 40,000+ satisfied customers and growing Comprehensive Inventory: Everything from rebuilt transmissions to overhaul kits, bearings, and pumps Expert Support: Our knowledgeable team ensures you get the right part the first time Fast Shipping: Reliable delivery to get you back on the water quickly Whether you're operating a pleasure yacht, a sportfishing boat, or a small commercial vessel, Diesel Pro Power has the Twin Disc MG-502 parts you need. Our selection of rebuilt transmissions, plate kits, gasket sets, bearings, and oil pumps is designed to help you maintain optimal performance and reliability on the water.
Twin Disc MG502 Marine Transmission Parts
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Introduction: Power and Precision for Smaller Marine Vessels
Specifications of the Twin Disc MG-502
Rebuilt Twin Disc MG-502 Transmissions: Reliable Performance, Tailored Gear Ratios
Available Gear Ratios for the Rebuilt Twin Disc MG-502 Transmissions
Key Benefits of Rebuilt MG-502 Units
Essential Parts for MG-502 Maintenance and Overhaul
Plate Kits for Twin Disc MG-502
Overhaul Gasket Sets for Twin Disc MG-502
Bearings for Twin Disc MG-502
Oil Pumps for Twin Disc MG-502
Rubber Blocks for Twin Disc MG-502
Marine Transmission Specifications & Applications of the Twin Disc MG502
Overview of the Twin Disc MG502 Marine Transmission
Key Specifications of the Twin Disc MG502
Common Marine Applications for the MG502
Most Common Engine Models Paired with the Twin Disc MG502
Cummins Marine Engines
Detroit Diesel Marine Engines
Perkins Marine Engines
Caterpillar Marine Engines
Yanmar Marine Engines
Volvo Penta Marine Engines (Older Series)
Advantages of the Twin Disc MG502 in Marine Use
Recommended Use Cases
Additional Resources
Why Choose Diesel Pro Power?
Conclusion: Ready to Power Your Vessel with Confidence
