Lower Unit Gearcase Seal Kit for Johnson/Evinrude 20–35 HP 2-Stroke Outboards – Replaces 396351, Sierra 18-2658, GLM 87680
Lower Unit Gearcase Seal Kit for Johnson/Evinrude 20–35 HP 2-Stroke Outboards – Replaces 396351, Sierra 18-2658, GLM 87680 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 20–35 HP 2-Stroke...
Lower Unit Gearcase Seal Kit for Johnson/Evinrude 20–35 HP 2-Stroke Outboards – Replaces 396351, Sierra 18-2658, GLM 87680 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Lower Unit Gearcase Seal Kit is intended for selected Johnson/Evinrude 2-cylinder Crossflow 20, 25, 30, and 35 HP outboard applications using a mechanical-shift gearcase with thru-prop exhaust. It provides the seals, gaskets, washers, and O-rings needed for lower-unit gearcase service.
The kit is identified as a replacement for Johnson/Evinrude OMC part number 396351. Catalog cross-references also identify Sierra 18-2658 and GLM 87680 with this application. Always compare the engine model, serial number, gearcase design, and original component before ordering.
- Replacement lower-unit gearcase seal kit for selected Johnson/Evinrude applications.
- Includes multiple oil seals, O-rings, washers, a rubber seal, and an impeller plate gasket.
- Helps renew sealing surfaces and reduce the risk of water intrusion or gear-lubricant leakage when installed correctly.
Part Number Matrix
These are cross-reference numbers associated with this seal-kit application. They are not the internal product identifier for this listing.
| Brand or source | Part number | Reference |
|---|---|---|
| Johnson/Evinrude OMC | 396351 | Original-equipment reference |
| Sierra | 18-2658 | Aftermarket cross-reference |
| GLM | 87680 | Aftermarket cross-reference |
Engine & Model Compatibility
The catalog application associated with part number 396351 is a Johnson/Evinrude 2-cylinder Crossflow gearcase used on selected 20–35 HP outboards. The available catalog evidence does not establish one universal year range for every model, so model and serial-number verification is required before purchase.
| Engine family | Rated HP | Stroke or design | Gearcase configuration | OEM reference | Verification requirement |
|---|---|---|---|---|---|
| Johnson/Evinrude 2-cylinder Crossflow | 20, 25, 30, or 35 HP | 2-stroke | Mechanical shift; thru-prop exhaust | 396351 | Confirm exact model and serial number |
Important: Horsepower alone does not confirm fitment. Do not apply this kit to a different gearcase design, shift system, cylinder configuration, or model without checking the correct parts listing or service information.
Technical Specs
- Product Type
- Lower unit gearcase seal kit
- Application
- Selected Johnson/Evinrude 20–35 HP 2-cylinder Crossflow outboards
- Gearcase type
- Mechanical shift with thru-prop exhaust
- Replacement reference
- Johnson/Evinrude OMC 396351
- Aftermarket references
- Sierra 18-2658; GLM 87680
- Construction
- Aftermarket replacement seal and gasket set
What’s in the Box
The cataloged contents for this seal-kit application are listed below. Individual seal and O-ring shapes may vary by location within the gearcase.
- 1 x Impeller plate gasket
- 6 x Oil seals
- 1 x Rubber seal
- 2 x Washers
- 11 x O-rings
Installation Notes
- Identify the exact engine model and serial number and obtain the appropriate service information before beginning work.
- Secure the outboard, place a drain pan under the lower unit, and remove the drain and vent screws to drain the gear lubricant.
- Disconnect the shift linkage as required and remove the fasteners securing the lower unit to the midsection.
- Lower the gearcase carefully and remove it from the engine.
- Disassemble the gearcase only as directed by the service manual for the specific model.
- Remove the old seals, O-rings, washers, and gaskets without damaging the shaft, bore, or housing sealing surfaces.
- Clean and inspect all sealing surfaces. Replace worn shafts, damaged housings, or other defective components before reassembly.
- Install the new components in the correct locations and orientation. Lubricate seals and O-rings with a compatible marine lubricant as specified by the service manual.
- Reassemble the gearcase and tighten fasteners to the manufacturer’s specified torque.
- Reinstall the lower unit, reconnect and adjust the shift linkage, and refill the gearcase with the specified marine gear lubricant.
- Fit new sealing washers where required, tighten the drain and vent screws, and check for leaks before returning the engine to service.
Troubleshooting & FAQ
How can I tell whether the gearcase seals need attention?
Milky or cream-colored gear lubricant can indicate water intrusion. Visible lubricant around the propeller shaft, driveshaft, shift-rod area, or drain and vent screws can also indicate a failed seal or sealing washer. Fishing line wrapped around the propeller shaft should be removed promptly because it can damage the seal and shaft.
Does this kit fit every Johnson/Evinrude 20–35 HP outboard?
No. The documented application is for selected 2-cylinder Crossflow models with the applicable mechanical-shift, thru-prop-exhaust gearcase. Verify the exact model, year, serial number, and gearcase configuration before ordering.
Why does the kit contain several O-rings and seals?
The seal kit covers the sealing points associated with this gearcase application. Install only the components specified for the particular model and gearcase being serviced; do not substitute parts solely because they appear similar.
Can I replace only one leaking seal?
A single seal can sometimes be replaced, but the correct repair depends on the failure and the condition of the other sealing components. Inspect the complete gearcase and follow the service procedure for the engine rather than replacing parts by appearance alone.
Is this an OEM product?
No. This is an aftermarket replacement kit. The listed Johnson/Evinrude, Sierra, and GLM numbers are customer-facing reference numbers used to identify the application.
Is installation suitable for a first-time repair?
Lower-unit seal replacement may require gearcase disassembly, special tools, seal drivers, and precise reassembly. Use the correct service manual and seek professional assistance if the required procedure or tooling is unfamiliar.
Safety & Important Info
- Confirm the model, serial number, stroke, gearcase design, and original seal-kit reference before ordering.
- Do not rely on horsepower alone to determine fitment.
- Use a service manual and follow the manufacturer’s torque, lubrication, adjustment, and sealing instructions.
- Inspect shafts, bores, housings, and fasteners for wear or damage before installing new seals.
- This is an aftermarket replacement, not an OEM component.
About Sea Sierra
- Marine Replacement Parts — We supply aftermarket components for servicing marine engines and lower units.
- Application-Focused Listings — Reference numbers and fitment details are provided to help you compare the replacement with your original part.
- Support for Correct Selection — When model or serial-number details are uncertain, verify the application before installation.
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