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Parts Catalog for Twin Disc MG520 Marine Transmissions
Rebuilt Twin Disc MG520 Marine Transmissions
Plate Kit For Twin Disc MG520 Marine Transmission
Gasket Kits For Twin Disc MG520 Marine Transmission
1. What is the Twin Disc MG520 marine gear?
The MG520 is a heavy-duty marine transmission designed by Twin Disc for commercial and industrial marine vessels. It delivers reliable power transfer between the engine and propeller.
2. What kind of vessels use the MG520?
It’s commonly used in tugboats, commercial fishing boats, ferries, offshore supply vessels, and heavy-duty workboats.
3. Is the MG520 suitable for recreational marine use?
Yes, but it’s primarily built for commercial-grade reliability. Recreational users benefit from its durability and torque-handling capabilities.
4. What is the gear ratio for the MG520?
The MG520 comes in various gear ratios. Refer to your nameplate or service manual for the exact ratio for your model.
5. Where is the serial number located on a Twin Disc MG520?
It’s stamped on the nameplate, typically mounted on the transmission housing. It includes the model, serial number, and gear ratio.
6. What kind of oil does the MG520 use?
SAE 30 or SAE 40 non-detergent oil is most commonly used. Refer to the service manual or Diesel Pro support for specific recommendations.
7. How often should I change the oil in the MG520?
Every 1,000 hours or annually—whichever comes first. More frequently if the unit operates under extreme conditions.
8. What are the signs of clutch plate wear?
Slipping under load, delayed engagement, burnt smell, or visible wear through inspection ports.
9. Can I rebuild the MG520 myself?
Yes, if you have the proper tools and mechanical experience. Diesel Pro Power offers complete rebuild kits.
10. How do I know which rebuild kit is right for my MG520?
Provide your serial number to Diesel Pro Power. They’ll match your model to the correct rebuild kit.
11. What’s included in a typical MG520 rebuild kit?
Clutch plates (friction and steel), seals, gaskets, bearings, bushings, thrust washers, and other essential internal parts.
12. How do I know when it’s time for an overhaul?
Every 5,000–7,000 hours of commercial use or sooner if slipping, overheating, or vibration occurs.
13. Can Diesel Pro Power help me identify the right parts?
Yes. Their technical support can identify and ship the right parts using your serial number or photos.
14. Is the MG520 transmission reversible?
Yes, it includes a hydraulic clutch system that enables forward and reverse propulsion.
15. How do I check the oil level in the MG520?
Use the dipstick on the top or side of the housing. Always check when the engine is off and the transmission is at operating temperature.
16. What’s the most common failure on the MG520?
Worn clutch plates and seal failures due to old oil or lack of maintenance.
17. Can I use synthetic oil in the MG520?
Use only if it meets Twin Disc’s marine transmission oil specs. Contact Diesel Pro for approved brands.
18. What causes metal shavings in MG520 oil?
Bearing or gear wear. Immediate inspection and overhaul are advised.
19. Can I just replace a single clutch plate?
No. Always replace full sets to ensure balanced engagement and pressure distribution.
20. Where can I buy MG520 parts online?
At Diesel Pro Power, offering aftermarket kits and same-day shipping.
21. Do you offer international shipping?
Yes, Diesel Pro ships MG520 parts worldwide with customs-ready documentation.
22. How long does a full rebuild take?
Typically 8–20 hours of labor depending on the mechanic’s experience and shop setup.
23. Do I need special tools for rebuilding the MG520?
Yes, including bearing pullers, micrometers, hydraulic presses, and seal drivers.
24. How much oil does the MG520 hold?
Varies by model and configuration, but generally 4–6 gallons. Always measure during refill.
25. What are common torque specs for MG520 fasteners?
Refer to the OEM service manual or Diesel Pro for a full torque chart.
26. How do I flush the MG520 transmission?
Drain oil, clean strainers, flush with light flushing oil or kerosene, then refill with fresh oil.
27. What causes MG520 overheating?
Clogged oil coolers, slipping clutch, low oil level, or internal friction from worn parts.
28. How do I align the MG520 to the engine?
Use a dial indicator to ensure concentric alignment and angular alignment within spec.
29. Can I use MG514C parts in an MG520?
No. They are different models with different internal designs. Always use MG520-specific parts.
30. What’s the warranty on Diesel Pro MG520 parts?
They come with a one year warranty.
31. What’s the difference between MG520 and MG520-1?
The -1 refers to a specific variant. Always check the full model number for accurate parts matching.
32. How often should I inspect the clutch assembly?
Every 2,000–3,000 hours or annually. Sooner if symptoms of slippage or engagement issues appear.
33. How do I identify a worn bearing?
Vibration, humming noise, or excess shaft play. Inspection requires disassembly.
34. Should I replace seals during every oil change?
Not necessary unless leaking. But all seals should be replaced during a rebuild.
35. Can I convert the MG520 for different gear ratios?
No. Gear ratios are fixed by design. Select the correct ratio at the time of purchase or overhaul.
36. Is there a difference between forward and reverse clutches?
Yes, although they operate on the same principle, each clutch pack may use different configurations.
37. How do I test for internal clutch pressure?
Use hydraulic gauges at designated ports. Refer to the service manual for test procedures and pressure specs.
38. What tools do I need to install the MG520?
Lifting hoist, alignment tools, torque wrench, seal drivers, and possibly custom jigs depending on your boat’s layout.
39. Can I reuse old clutch plates if they look good?
No. Even minor glazing or thickness variation can cause engagement issues.
40. Does the MG520 have a filter or strainer?
Yes, many versions have an internal oil strainer that should be cleaned at regular service intervals.
41. How do I know if the oil cooler is working?
Check return line temperature. A significant temperature rise may indicate a clogged or failing cooler.
42. Can MG520 parts be sourced from local dealers?
Some can, but Diesel Pro offers faster access and often better pricing on complete aftermarket kits.
43. Can I run the MG520 without a load for testing?
Yes, but never engage gear without oil pressure and fluid at operating temperature.
44. Can I install the MG520 vertically or at an angle?
Follow OEM mounting guidelines. Incorrect installation angle can cause oil starvation.
45. What happens if I overfill the MG520?
Foaming, overheating, and internal pressure can damage seals. Always fill to the dipstick mark.
46. Can I run a MG520 on land without a shaft?
Only for brief testing and never under load. Lack of load can lead to abnormal heat buildup.
47. Where can I find videos on MG520 repairs?
Diesel Pro’s YouTube channel will soon include step-by-step tutorials for rebuilds, diagnostics, and maintenance.
48. Do you sell complete rebuilt MG520 transmissions?
Yes. Diesel Pro offers rebuilt units for those who prefer replacement over in-house repair.
49. What’s the cost of a full rebuild vs replacement?
Rebuilds typically cost less than 50% of a new unit. Kits range from a few hundred to a couple thousand dollars depending on scope.
50. Where can I get more help?
Contact Diesel Pro Power’s expert team for guidance, part selection, and troubleshooting. Visit: https://dieselpro.com/help
Parts Catalog for Twin Disc MG520 Marine Transmissions
Rebuilt Twin Disc MG520 Marine Transmissions
Plate Kit For Twin Disc MG520 Marine Transmission
Gasket Kits For Twin Disc MG520 Marine Transmission
