Lower Unit Gearcase Seal Kit for Johnson/Evinrude 40–75 HP Outboards – Cross-References 5000309, 777558, Sierra 18-8383
Lower Unit Gearcase Seal Kit for Johnson/Evinrude 40–75 HP Outboards – Cross-References 5000309, 777558, Sierra 18-8383 is backordered and will ship as soon as it is back in stock.
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Lower Unit Gearcase Seal Kit for Johnson/Evinrude 40–75 HP Outboard...
Lower Unit Gearcase Seal Kit for Johnson/Evinrude 40–75 HP Outboards – Cross-References 5000309, 777558, Sierra 18-8383 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket lower unit gearcase seal kit is designed for selected Johnson and Evinrude outboards with large-housing gearcases. It helps renew the seals, O-rings, washers, and gaskets used during lower-unit service and helps protect the gearcase from water intrusion and lubricant leakage.
The kit is listed for Johnson/Evinrude 3-cylinder 60, 65, 70, and 75 HP models from 1978–2001; 3-cylinder 50 HP models from 1995–2001; and Evinrude E-TEC 40, 50, and 60 HP models from 2004 onward. Always compare the engine model, year, gearcase housing, and original component dimensions before ordering.
- Complete lower-unit gearcase seal service kit
- For selected Johnson/Evinrude outboards
- Includes oil seals, O-rings, gasket, and drain/fill plug washers
- Aftermarket replacement for service applications
OEM and Aftermarket References
Use the references below to help compare this kit with the part listed for your outboard. These numbers are reference identifiers only; they do not replace verification of the complete engine and gearcase application.
| Reference Type | Brand | Reference |
|---|---|---|
| OEM reference | Evinrude / Johnson / OMC / BRP | 5000309 |
| OEM reference | Evinrude / Johnson / OMC / BRP | 777558 |
| Aftermarket reference | Sierra Marine | 18-8383 |
| Aftermarket reference | Sierra Marine | 18-2660 |
| Aftermarket reference | SEI Marine | 95-366-11K |
| Aftermarket reference | OBR | JE-934 |
| Aftermarket reference | Mallory Marine | 9-74103 |
| Aftermarket reference | GLM | 87601 |
Engine and Model Compatibility
Fitment is based on the application ranges supplied for this product. Confirm the exact model and gearcase configuration before installation.
| Brand | Engine Configuration | Rated HP | Stroke | Years | Housing / Notes |
|---|---|---|---|---|---|
| Johnson / Evinrude | 3-cylinder | 60, 65, 70, 75 HP | 2-Stroke | 1978–2001 | Verify large-housing gearcase |
| Johnson / Evinrude | 3-cylinder | 50 HP | 2-Stroke | 1995–2001 | Verify large-housing gearcase |
| Evinrude E-TEC | E-TEC | 40, 50, 60 HP | 2-Stroke | 2004 onward | Verify the exact model and gearcase housing |
Technical Specifications
- Product Type
- Lower unit gearcase seal kit
- Application
- Selected Johnson/Evinrude outboard gearcases
- Engine Type
- 2-stroke outboards, including listed Evinrude E-TEC applications
- Installation
- Replacement service part; professional installation is recommended
- Product Status
- Aftermarket replacement, not an OEM-manufactured component
What's in the Box
The company parts listing identifies the following contents and quantities:
- 2 x Oil Seal, Sierra reference 18-2001; OEM 330137
- 1 x Oil Seal, Sierra reference 18-2059; OEM 321466
- 1 x Oil Seal, Sierra reference 18-2064; OEM 332205
- 1 x Exhaust Leg Seal, Sierra reference 18-2537; OEM 324937
- 1 x Shift Housing Gasket, Sierra reference 18-2855; OEM 314082
- 2 x Drain/Fill Plug Washer, Sierra reference 18-4248; OEM 311598
- 1 x O-Ring, Sierra reference 18-7120; OEM 307853
- 1 x O-Ring, Sierra reference 18-7127; OEM 313446
- 1 x O-Ring, Sierra reference 18-7128; OEM 313754
- 1 x O-Ring, Sierra reference 18-7137; OEM 318372
- 2 x O-Ring, Sierra reference 18-7145; OEM 333572
- 1 x O-Ring, Sierra reference 18-7174; OEM 326649
- 4 x O-Ring, Sierra reference 18-7475; OEM 332584
- 1 x O-Ring, Sierra reference 18-7158; OEM 309731
- 1 x O-Ring, Sierra reference 18-7481; OEM 324981
Installation Notes
- Disconnect the battery and secure the outboard according to the manufacturer's service instructions.
- Drain the gearcase lubricant and remove the lower unit using the correct service procedure for the engine.
- Disassemble the gearcase only as necessary to access the applicable seals, O-rings, washers, and gaskets.
- Remove the old sealing components and clean the seal bores and mating surfaces. Inspect shafts, bores, threads, and housing surfaces for wear or corrosion.
- Lightly lubricate compatible seals and O-rings before installation. Use suitable drivers and install each component squarely without damaging the sealing lip.
- Reassemble the gearcase using the manufacturer's torque specifications and any required sealant or lubricant procedures.
- Refit the lower unit, reconnect the shift linkage, and fill the gearcase with the recommended lubricant.
- Check for water intrusion and lubricant leakage before returning the boat to service.
Troubleshooting and FAQ
How do I confirm that this kit fits my outboard?
Match the exact engine brand, model, horsepower, year, stroke, and gearcase housing to the compatibility information above. Compare the original seals and O-rings with the kit contents before installation. Horsepower and year alone are not sufficient for every application.
What are common signs of failed lower-unit seals?
Common signs include milky or cloudy gear lubricant, visible lubricant around the propeller shaft or water-pump area, water entering the gearcase, or repeated lubricant loss. Identify and correct the source of the leak before continued operation.
Is this an OEM kit?
No. This is an aftermarket replacement kit supplied for the listed applications. The OEM and aftermarket numbers shown above are reference numbers for comparison and fitment research.
Does the kit include every part needed for any lower-unit repair?
The kit contains the seals, O-rings, gasket, and washers listed in the box contents. It does not represent a complete gearcase rebuild and does not include unrelated bearings, shafts, gears, lubricant, or special tools.
Safety and Important Information
- Confirm the exact engine model, year, horsepower, stroke, and gearcase housing before ordering.
- Do not rely on a part number alone when different housing or model configurations are possible.
- Inspect all mating surfaces and shafts during service; worn components can cause a new seal to leak.
- Follow the engine manufacturer's service manual for disassembly, torque, lubricant, and sealant requirements.
- Professional installation is recommended for safe and reliable operation.
About Sea Sierra
- Marine Parts Focus — Replacement components for common outboard and marine service applications.
- Application-Conscious Listings — Fitment information is organized by engine configuration, horsepower, stroke, and year range where available.
- Service Support — Compare your original part and exact engine details before installation.
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