Lower Unit Gasket Seal Kit – Fits Mercury/Mariner 25-30HP (Replaces 27-8M0089639, 95220A1)
Lower Unit Gasket Seal Kit – Fits Mercury/Mariner 25-30HP (Replaces 27-8M0089639, 95220A1) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Lower Unit Gasket Seal Kit – Fits Mercury/Mariner 25-30HP (Replaces...
Lower Unit Gasket Seal Kit – Fits Mercury/Mariner 25-30HP (Replaces 27-8M0089639, 95220A1) is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit Gasket Seal Kit is designed for Mercury/Mariner 2-stroke outboard engines, specifically covering 25 HP, 30 HP, and 25 Jet models manufactured between 1984 and 1991. It provides all the necessary components to reseal the gearcase, preventing water intrusion and oil leaks.
It serves as a direct aftermarket replacement for Mercury part numbers 27-8M0089639, 95220A1, 804908A01, and 27-8M0089636, and is equivalent to Yamaha references such as 689-W0001-22-00.
- Installs in the lower unit (gear case) to restore watertight integrity.
- Includes a complete set of gaskets, seals, and O-rings for a full service.
- Essential for routine lower unit maintenance, repairs, or rebuilds.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/Mariner | 27-8M0089639 |
| Mercury/Mariner | 95220A1 |
| Mercury/Mariner | 804908A01 |
| Mercury/Mariner | 27-8M0089636 |
| Mercury/Mariner | 41899M |
| Mercury/Mariner | 27-41899M |
| Yamaha | 689-W0001-22-00 (Cross-Reference) |
| Yamaha | 689-W0001-21-00 (Cross-Reference) |
| Yamaha | 689-W0001-C1-00 (Cross-Reference) |
| Yamaha | 689-W0001-C2-00 (Cross-Reference) |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury/Mariner owners, this kit fits a range of 2-cylinder, 430cc models from the mid-1980s to the early 1990s. Please verify your specific model code and year against the list.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 25/25 JET/30HP (2 CYL/430CC) | 25–30 | 2-Stroke | 1984–1991 | 27-8M0089639, 95220A1 | International models |
| Mercury/Mariner | 25 Jet | 25 Jet | 2-Stroke | 1984–1991 | 27-8M0089639, 95220A1 | 2 cylinder |
| Mercury/Mariner | 25ELK, 25ESK, 25LK, 25SK | 25 | 2-Stroke | 1985 | 41899M, 27-41899M | |
| Mercury/Mariner | 30ELN, 30ESN | 30 | 2-Stroke | 1984 | 41899M, 27-41899M | |
| Mercury/Mariner | 30ELK, 30ESK | 30 | 2-Stroke | 1985 | 41899M, 27-41899M | |
| Mercury/Mariner | 25ELJ, 25ESJ, 25LJ, 25SJ | 25 | 2-Stroke | 1986 | 41899M, 27-41899M | |
| Mercury/Mariner | 30ELJ, 30ESJ | 30 | 2-Stroke | 1986 | 41899M, 27-41899M | |
| Mercury/Mariner | 25ELH, 25ESH, 25LH, 25SH | 25 | 2-Stroke | 1987 | 41899M, 27-41899M | |
| Mercury/Mariner | CV30ELF | 30 | 2-Stroke | 1989 | 41899M, 27-41899M | |
| Mercury/Mariner | CV25ELD, CV25EMLD, CV30ELD | 25–30 | 2-Stroke | 1990 | 41899M, 27-41899M | |
| Mercury/Mariner | C25ELHP, C25ELRP, C30ELRP, C30ERP | 25–30 | 2-Stroke | 1991 | 41899M, 27-41899M |
Technical Specs
- Product Type
- Lower Unit Gasket Seal Kit
- Installation
- Lower Unit/Gear Case
Installation Notes
- Place a drain pan under the lower unit and remove the upper (vent) and lower drain screws to empty the gear oil.
- Remove the bolts securing the lower unit to the engine's midsection.
- Carefully lower and detach the gearcase assembly. You may need to disconnect the shift shaft linkage first.
- Disassemble the lower unit as required to access the old seals and gaskets (e.g., water pump housing, bearing carriers).
- Thoroughly clean all mating surfaces, removing any old gasket material or sealant residue. A plastic scraper can prevent gouging aluminum surfaces.
- Install the new gaskets, seals, and O-rings from the kit. Lightly oil new seals to ease installation and prevent damage.
- Reassemble the lower unit components, torquing all fasteners to the manufacturer's specifications found in your service manual.
- Reattach the lower unit to the engine, ensuring the driveshaft, water tube, and shift shaft are correctly aligned.
- Using a gear lube pump, refill the gearcase through the bottom drain hole until lube flows from the upper vent hole.
- Install the upper vent screw, then quickly remove the pump and install the lower drain screw. Always use new washers on the drain screws.
Troubleshooting & FAQ
How do I know if my lower unit gaskets are failing?
The most common sign is "milky" or cloudy gear oil, which indicates water has mixed with the lubricant. Other symptoms include visible oil leaks from the propeller shaft, driveshaft, or shift shaft seals, or a persistent drop in the gear lube level.
Does this kit fit all 25-30HP Mercury engines?
No. This kit is specifically for the 2-stroke, 2-cylinder models manufactured between 1984–1991. It is critical to check your engine's model, serial number, and year against our compatibility chart to ensure a correct fit.
What are the signs of a failed lower unit seal?
Telltale signs include finding water-contaminated (milky) gear lube, observing oil drips from the seals around the propeller or driveshaft, or noticing the gear oil level is consistently low. Any of these symptoms warrant an inspection and likely a reseal.
Are any special tools required for installation?
While many steps can be completed with standard mechanic's tools, a proper and safe installation often requires specialized equipment such as a seal puller, a bearing carrier puller, and a torque wrench. We strongly recommend consulting your engine's factory service manual for detailed procedures.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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