5006373 Seal Kit Lower Unit Gearcase for Johnson Evinrude | JLM Marine

Seal Kit Lower Unit Gearcase for Johnson Evinrude – 5006373

This lower unit gearcase seal kit is designed to fit a wide range of Johnson and Evinrude outboard motors, including E-Tec models from 75 HP to 300 HP and various V-4, V-6, and V-8 engines manufactured from the mid-1970s through the mid-1990s. It provides a complete sealing solution for lower unit maintenance and repair across multiple displacement classes (1.6L to 4.0L).

This kit directly replaces OEM part numbers 5006373, 5000411, 439141, 438278, 396354, 396353, and crosses to aftermarket numbers including Sierra 18-8384, 18-2623, Mallory 9-74106, and GLM 87600. It consolidates superseded part numbers 0437752 and 0437753 for broad application coverage.

• Complete gearcase seal kit with all components shown in product images
• Fits both standard and counter-rotation models where specified
• Covers commercial (Comm) and recreational outboard applications

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here's a guide to help you identify your engine's serial/model: Johnson Serial Number Guide.

Technical Specifications

Package Contents

• 1× Gearcase Seal Kit
• The package contains all the parts shown in the picture.

Installation Guide

1. Disconnect the battery and remove the lower unit from the outboard motor following manufacturer procedures. Drain all gearcase oil completely.
2. Remove the old propeller shaft and carefully extract the drive shaft from the gearcase. Inspect all components for wear or damage.
3. Remove all old seals, O-rings, and gaskets from the gearcase housing using appropriate seal removal tools. Clean all sealing surfaces thoroughly with a degreaser and lint-free cloth.
4. Install the new propeller shaft seals using a seal driver or appropriate-sized socket, ensuring they seat squarely and to the correct depth. Apply marine-grade grease to seal lips.
5. Install new O-rings and gaskets in their proper locations, lightly lubricating with gearcase oil or assembly grease. Do not overstretch O-rings during installation.
6. Reinstall the drive shaft and propeller shaft, ensuring all components align correctly. Replace any bearings or washers as indicated in your service manual.
7. Reassemble the lower unit to the motor housing using a new gasket and applying appropriate sealant where specified. Torque all fasteners to manufacturer specifications.
8. Refill the gearcase with the correct grade and quantity of lower unit gear oil through the fill hole until oil appears at the vent hole. Install both drain and vent plugs with new washers.
9. Reinstall the propeller with a new propeller shaft washer and cotter pin. Check that the propeller spins freely without binding.
10. Reconnect the battery and perform a visual inspection for any oil leaks around seal areas. Run the engine in a test tank or on the water for 10-15 minutes.
11. After the test run, recheck the gearcase oil level and inspect all seal areas for leaks. Top off oil if necessary.
12. Monitor the lower unit for proper operation and check oil level after the first few hours of use. Regular maintenance intervals should be followed per manufacturer recommendations.

Troubleshooting & FAQ

Q: How do I confirm this seal kit fits my specific Johnson or Evinrude motor?
A: Cross-reference your engine's model, horsepower, and year with the compatibility table above. You can also verify by matching your current OEM part number (found on the old seal kit or in your service manual) with the part numbers listed in our cross-reference table. If your model year or configuration falls outside the listed ranges, contact us before purchasing.

Q: What are the signs that my lower unit seals need replacement?
A: Common symptoms include visible oil leaking from the propeller shaft area, milky or discolored gearcase oil (indicating water intrusion), excessive oil consumption, or unusual noise from the lower unit. If you notice any of these signs, inspect and replace seals promptly to prevent internal damage.

Q: How often should I replace lower unit seals?
A: Seal replacement intervals depend on usage and operating conditions. As a general guideline, inspect seals during annual service or every 100 hours of operation. Replace seals if you observe any leakage, perform major lower unit service, or after prolonged storage. Saltwater and heavy-duty use may require more frequent replacement.

Q: Does this kit include all seals needed for a complete lower unit rebuild?
A: This kit includes all the seals and O-rings shown in the product images, which typically cover the primary gearcase sealing points. For a complete lower unit rebuild, you may also need bearings, shims, and additional gaskets depending on your motor's condition. Refer to your service manual for a comprehensive parts list.

Q: Can I install this seal kit myself or do I need professional help?
A: Lower unit seal replacement requires mechanical aptitude, specialized tools (seal drivers, bearing pullers, torque wrench), and familiarity with outboard service procedures. If you have experience with marine maintenance and access to a service manual, DIY installation is feasible. Otherwise, professional installation is recommended to ensure proper assembly and prevent costly damage.

Q: Is this an OEM part or an aftermarket replacement?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.