26-41365A3 Lower Unit Seal Kit for Mercury Mariner | JLM Marine

Lower Unit Seal Kit for Mercury Mariner 6, 8, 9.9, 10, 15 HP Outboard Motors

This comprehensive lower unit seal kit is engineered for Mercury Mariner 2-stroke and 4-stroke outboard motors ranging from 6 HP to 15 HP. Designed to restore lower unit integrity and prevent water intrusion, this kit fits models from 1986 and up, including select Force and Sears engines. It provides a complete rebuild solution for maintaining your outboard's water pump and lower unit sealing system.

This aftermarket replacement kit directly replaces OEM part numbers 26-41365A3, 46-42089A3, 46-42089A4, 46-42089A5, 46-42040A5, 46-42040T5, and 46-42040A1, as well as Sierra Marine 18-3149 and 18-3149-2. It consolidates multiple OEM and aftermarket part numbers for broad compatibility across Mercury Mariner outboard models.

• Complete water pump and seal rebuild kit with all necessary gaskets, seals, and hardware
• Fits both 2-stroke and 4-stroke Mercury Mariner models from 6 HP to 15 HP
• Includes premium impeller, housing assembly, face plate, base assembly, and dual oil seals

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 Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This complete rebuild kit includes all components shown in the product images:

• 1× Water Pump Impeller (47-42038Q02, 420382, 47-42038-2)
• 1× Impeller Key
• 1× Housing Assembly (42089A2)
• 1× Face Plate (42200)
• 1× Gasket (19202, 192043)
• 1× Water Pump Base Assembly (42040T5)
• 2× Oil Seal (413651)
• 2× Washers
• 1× Quad Ring (822236)
• 1× Screw

Note: The package contains all parts shown in the product images.

Installation Guide

1. Prepare your workspace: Disconnect the fuel line and shift the engine into neutral. Remove the propeller and drain the lower unit gear oil completely.
2. Remove the lower unit: Disconnect the shift linkage and unbolt the lower unit from the midsection. Carefully separate the lower unit assembly.
3. Disassemble the water pump: Remove the old water pump housing, face plate, and impeller. Clean all mating surfaces thoroughly to remove old gasket material and debris.
4. Inspect components: Check the drive shaft and water tube for wear or damage. Replace any corroded or damaged parts before reassembly.
5. Install new oil seals: Carefully press the new oil seals (413651) into the lower unit housing. Lubricate seals with marine-grade grease before installation.
6. Install the water pump base: Position the new water pump base assembly (42040T5) with the provided gasket. Ensure proper alignment with the drive shaft.
7. Install the impeller: Lubricate the new impeller with glycerin or soapy water. Insert the impeller key and slide the impeller onto the drive shaft, rotating blades in the correct direction.
8. Install housing and face plate: Place the new housing assembly (42089A2) over the impeller, ensuring blades are properly seated. Install the face plate (42200) with a new gasket.
9. Reassemble the lower unit: Install washers and quad ring (822236) as shown in your service manual. Reconnect the shift linkage and align the water tube with the pump intake.
10. Bolt the lower unit: Reinstall all mounting bolts in the correct sequence and torque to manufacturer specifications. Do not overtighten.
11. Refill gear oil: Fill the lower unit with fresh marine gear oil until it flows from the upper vent hole. Install drain and vent plugs with new washers.
12. Test operation: Reinstall the propeller and run the engine in a test tank or on the water. Verify strong water pump flow from the telltale and check for leaks.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury Mariner engine?
A: Check the compatible engine models table above and match your engine's HP rating, stroke type (2-stroke or 4-stroke), year, and serial number. Serial numbers are typically stamped on the engine mounting bracket or swivel bracket.

Q: How often should I replace the water pump and seals?
A: Mercury recommends replacing the water pump impeller and seals every 2-3 years or 200-300 hours of operation, whichever comes first. Replace immediately if you notice overheating or reduced water flow from the telltale indicator.

Q: What are the signs that my lower unit seals are failing?
A: Common symptoms include milky or contaminated gear oil (indicating water intrusion), visible oil leaks around the propeller shaft, difficulty shifting gears, or unusual noise from the lower unit during operation.

Q: Can I use this kit on Bigfoot models?
A: No, this kit is designed for standard (Non-Bigfoot) Mercury Mariner models only. Bigfoot models require different part numbers due to their larger gearcase design.

Q: Do I need any special tools to install this seal kit?
A: Basic hand tools are sufficient for most installations, but a seal driver set, torque wrench, and gear oil pump are recommended. Refer to your Mercury service manual for specific torque specifications and procedures.

Q: OEM vs. Aftermarket?
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.