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Parts Catalog for Twin Disc MG5090A Marine Transmissions
Plate Kit For Twin Disc MG5090A Marine Transmission
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General Overview FAQs For Twin Disc MG-5090A Marine Gear
- What is the Twin Disc MG-5090A marine transmission?
The MG-5090A is a marine gear system designed by Twin Disc to handle power transfer from marine engines to propellers. It includes hydraulic clutch packs and reduction gears, offering reliable shifting and efficient torque transfer in both recreational and commercial marine applications.
- What type of boats typically use the MG-5090A?
This gear is commonly found in commercial fishing boats, small tugboats, ferries, pilot boats, pleasure crafts, and other inshore and nearshore work vessels. It’s especially valued in fleets needing reliability and easy serviceability.
- What makes the MG-5090A different from other Twin Disc models?
It is a compact, mid-range marine gear designed with an optimized clutch size, a robust gear housing, and a range of reduction ratios. The “A” designation refers to specific engineering and hydraulic configuration improvements over earlier versions.
- Is the MG-5090A still in production?
While still supported, this model is often found in legacy fleets. Twin Disc has produced newer models, but Diesel Pro Power offers completely rebuilt MG-5090A units and all service parts.
- Where can I find the serial number and data tag?
The serial number is typically located on a riveted metal data tag on the main housing, near the top or side of the transmission case. This tag also includes the model number and reduction ratio.
Compatibility & Sizing FAQs For Twin Disc MG-5090A Marine Gear
- What is the input horsepower rating for the MG-5090A?
It varies based on reduction ratio and duty cycle, but generally supports up to 500 HP in light-duty applications and around 400 HP in continuous commercial use.
- What are the available reduction ratios?
Common ratios include 2.00:1, 2.47:1, and 2.95:1. Always verify your vessel’s tag to confirm the exact ratio before ordering parts.
- Can I use this transmission with both gasoline and diesel engines?
Yes, as long as the engine power, torque, and RPM fall within the transmission’s rated limits. Diesel is more common, but the MG-5090A is versatile.
- Does it work with right-hand or left-hand propeller rotation?
The MG-5090A supports both, but configurations are specific—some versions require setup changes to accommodate left-hand rotation.
- What shaft size does the MG-5090A support?
It typically supports a 2” or 2.5” output shaft, but check your specific model. Shaft coupling types also vary by setup.
Oil, Fluids & Filters FAQs For Twin Disc MG-5090A Marine Gear
- What type of oil does the MG-5090A use?
Use high-quality marine transmission oil or SAE 30 non-detergent engine oil that meets Twin Disc or equivalent specifications. Diesel Pro Power provides pre-approved fluid options.
- How much oil does it hold?
Approximate oil capacity is 5.5 to 6 quarts (5.2–5.7 liters), depending on cooler size and hose configuration.
- How often should I change the oil?
Every 250 to 500 hours under normal conditions, or more frequently in heavy-duty or commercial operation.
- Can I use synthetic oil?
Only if it meets all viscosity and additive requirements for marine gear use. Consult your oil supplier and verify Twin Disc compatibility.
- How do I check the oil level?
With the engine idling in neutral, check the dipstick located on the top cover. Oil should be within the marked “full” range.
- What color should the oil be?
Clean oil should be light amber or clear. If it appears milky (indicating water), black (burnt), or gritty (contaminated), change it immediately.
- How often should I replace the oil filter?
Every time you change the oil. A fresh filter ensures proper oil flow and protects the clutches and gears.
- Where is the oil filter located?
The spin-on filter is mounted near the top or side of the housing. It’s easily accessible for replacement using a standard oil filter wrench.
Performance & Troubleshooting FAQs For Twin Disc MG-5090A Marine Gear
- Why does the gear slip when in forward or reverse?
Slipping could be caused by low oil pressure, worn clutch plates, or incorrect control linkage adjustment. Start with checking hydraulic pressure and oil condition.
- Why is the transmission slow to engage?
Delayed engagement may indicate worn clutches, low pressure, air in the hydraulic system, or issues with control signal timing.
- Why do I hear grinding or whining noises?
This often signals bearing or gear wear. If it’s a high-pitched whine, it may be due to cavitation or misalignment. A low grind often indicates gear tooth damage.
- Why is the transmission overheating?
Common causes include a fouled oil cooler, low oil level, or excessive clutch slippage under load. Check coolant flow and flush the cooler.
- Why is there vibration when under load?
Propeller imbalance, misalignment, or worn engine mounts can all cause vibration. Clutch pack issues may also contribute.
- What does it mean if I hear a “clunk” when shifting?
A heavy mechanical noise during shifting may result from improper idle RPM, control delay, or hardened clutch engagement. Check RPM specs and control cable tension.
Installation & Alignment FAQs For Twin Disc MG-5090A Marine Gear
- How is the MG-5090A mounted to the engine?
It uses a SAE housing interface (usually SAE #1 or #2) and a flex plate or drive damper depending on engine configuration.
- How critical is engine-transmission alignment?
Extremely critical. Misalignment causes premature clutch wear, oil leaks, and shaft bearing damage. Use a dial indicator and straightedge to ensure alignment.
- What should I torque the mounting bolts to?
Refer to Twin Disc’s service manual for precise values. In general, torque ranges from 45–90 ft-lbs depending on bolt size.
- Can I install this transmission in a vertical position?
No, the MG-5090A is designed for horizontal mounting only. Installing it vertically will lead to oil starvation and clutch damage.
- What size propeller is best matched to this gear?
The correct propeller size depends on engine horsepower and reduction ratio. Consult a marine propeller specialist or use Diesel Pro Power’s prop sizing assistance.
Clutch & Hydraulic System FAQs For Twin Disc MG-5090A Marine Gear
- What type of clutch does this transmission use?
It uses a hydraulic multi-disc wet clutch system for both forward and reverse engagement.
- How do I know if the clutch is worn out?
Symptoms include slipping under load, black oil, harsh engagement, and reduced RPM performance. Internal inspection is required for confirmation.
- Can the clutch be rebuilt on-board?
Yes, if you have experience with marine transmissions and access to the correct tools and rebuild kit. Diesel Pro Power offers complete clutch kits and gaskets.
- What hydraulic pressure should I see during clutch engagement?
Typical operating pressure is around 250–300 PSI. Always verify with a pressure gauge installed at the test port.
- How do I test the hydraulic system?
Use a tee-fitting and 0–500 PSI gauge to measure pressure while shifting through neutral, forward, and reverse.
- What could cause a sudden loss of hydraulic pressure?
Low oil level, failed pump gears, worn valve body components, or clogged filters can all contribute to sudden pressure drops.
Controls & Linkages FAQs For Twin Disc MG-5090A Marine Gear
- What type of control systems can be used?
It supports both mechanical lever cables and electronic control systems such as the Twin Disc EC300. Some vessels use integrated throttle-shift controls.
- How do I adjust shift linkage?
Ensure the shift lever fully travels into the detents for forward, neutral, and reverse. Adjust cable tension and bracket length as needed.
- Can a damaged shift cable cause clutch problems?
Yes, if the shift lever does not fully engage the clutch valve, it may cause slippage or delayed response.
- What should I do if the control lever won’t stay in gear?
Check the detent spring and ball in the clutch valve body. If worn, it won’t hold the lever in position.
- Is control calibration needed for electronic systems?
Yes. Follow the manufacturer’s control setup procedure, which usually involves a learning sequence and calibration through the control panel.
Maintenance & Lifecycle FAQs For Twin Disc MG-5090A Marine Gear
- What’s the expected service life of this transmission?
With proper maintenance, many MG-5090A units last over 10,000 hours. Regular oil changes and correct alignment are key.
- How often should I inspect the clutch packs?
Every 2,000–3,000 hours or sooner if performance drops. Clutch packs should be inspected visually for wear and warping.
- How often should I flush the cooler?
Annually, or every 1,000 hours. More often if you operate in silty or tropical water conditions.
- Can I overhaul the MG-5090A myself?
Yes, with experience and proper parts. Diesel Pro Power sells full overhaul kits including gaskets, bearings, seals, and clutch discs.
- What’s included in a rebuild kit from Diesel Pro Power?
Gaskets, seals, bearings, friction discs, steel plates, o-rings, and optional control components. OEM-matching quality and warranty are included.
- What should I do during off-season lay-up?
Drain and refill oil, fog the gear with protective oil, rotate the input shaft monthly, and protect vent openings from humidity.
- Can I upgrade the cooler for higher flow capacity?
Yes. Diesel Pro Power offers higher-capacity aftermarket coolers if your vessel is experiencing high oil temps.
Purchasing & Support FAQs For Twin Disc MG-5090A Marine Gear
- Where can I get replacement parts fast?
DieselPro.com offers same-day shipping on in-stock MG-5090A parts, rebuild kits, filters, and complete transmissions.
- Do you offer rebuilt MG-5090A units?
Yes. Diesel Pro Power carries fully remanufactured MG-5090A transmissions tested and ready to install, with a 1-year warranty.
- Who can I talk to if I need help diagnosing an issue?
Diesel Pro Power offers expert tech support for all MG-5090A issues. Call, email, or chat with a marine gear specialist to get personalized service.
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