8M0181315 Maintenance Kit for Mercury 4HP 5HP 6HP 4-Stroke | JLM Marine

Maintenance Kit for Mercury 4HP 5HP 6HP 4-Stroke Outboard Motors

This comprehensive maintenance kit is specifically designed for Mercury 4-Stroke outboard motors rated at 4HP, 5HP, and 6HP with carbureted fuel systems. Engineered to fit models with serial numbers 0R411838 and above, this kit provides all essential service components to keep your engine running smoothly and reliably season after season.

OEM Reference Number: 8M0181315. This aftermarket kit delivers the same specifications and quality as the original equipment, ensuring proper fit and performance for routine maintenance intervals.

• Complete service bundle including impeller, thermostat, fuel filter, seals, gaskets, and anode
• Fits carbureted 4-stroke Mercury motors (4/5/6 HP, serial 0R411838 & above)
• Includes specialized gear oil pump for convenient fluid changes

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 maintenance kit includes the following components for complete engine servicing:

• Water Pump Components:
  • 161543 – Impeller × 1
  • 16160004 – Gasket × 1
  • 16158009 – Gasket × 1
  • 16156 – Gasket × 1
  • 16159 – Guide Plate × 1
  • 16157 – Insert × 1
  • 16155 – Pin × 1
  • 16826 – Gasket × 4
  • 161251 – Screw × 4
• Thermostat Assembly:
  • 804540 – Thermostat × 1
  • 27-853702005 – Thermostat Gasket × 1
• Fuel System:
  • 35-8M0157133 – Fuel Filter × 1
• Seals & Gaskets:
  • 26-16130 – Oil Seal × 1
  • 8035161 – Gasket × 1
  • 25-16131 – O-ring × 1
  • 12-191833 – Drain Gasket × 2
  • 27-95220 – Drain Gasket × 2
• Hardware & Accessories:
  • 8150264 – Cotter Pin × 1
  • 875208 – Anode × 1
  • 24OP149 – Gear Oil Pump × 1 (for convenient gear oil changes)

Installation Guide

1. Preparation: Disconnect the fuel line and remove the lower unit from the outboard motor following your engine's service manual. Clean the mounting surfaces thoroughly.
2. Water Pump Disassembly: Remove the old water pump housing and carefully extract the old impeller, noting its orientation. Inspect the pump housing for scoring or damage.
3. Install New Impeller: Lubricate the new impeller (161543) with glycerin or soapy water and insert it into the housing with blades oriented correctly. Install the guide plate (16159), insert (16157), and pin (16155).
4. Gasket Replacement: Replace all water pump gaskets (16160004, 16158009, 16156, and 16826) ensuring proper alignment. Torque screws (161251) to manufacturer specifications in a cross pattern.
5. Thermostat Service: Remove the old thermostat and gasket from the cylinder head. Install the new thermostat (804540) with gasket (27-853702005), ensuring correct orientation with the spring facing the proper direction.
6. Fuel Filter Replacement: Locate the inline fuel filter and replace it with the new filter (35-8M0157133). Ensure fuel flow direction arrows point toward the engine.
7. Lower Unit Seals: Replace the oil seal (26-16130), O-ring (25-16131), and gasket (8035161) on the lower unit drive shaft and propeller shaft as needed. Apply marine-grade grease to seal lips.
8. Drain Plug Gaskets: Install new drain gaskets (12-191833 and 27-95220) on both the upper and lower drain plugs. Do not over-tighten drain plugs.
9. Gear Oil Service: Use the included gear oil pump (24OP149) to refill the lower unit with the appropriate gear oil until it flows from the upper vent hole. Install both drain plugs with new gaskets.
10. Anode Replacement: Remove the old sacrificial anode and install the new anode (875208). Ensure metal-to-metal contact for proper corrosion protection.
11. Reassembly: Reinstall the lower unit to the engine, aligning the water tube and shift linkage carefully. Torque all mounting bolts to specification.
12. Final Check: Reconnect the fuel line, start the engine in a test tank or on muffs, and verify water pump flow and proper operation. Check for leaks around all serviced areas.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my specific Mercury outboard?
A: Verify that your engine is a 4-stroke carbureted Mercury rated at 4HP, 5HP, or 6HP with a serial number of 0R411838 or higher. Cross-reference the OEM part number 8M0181315 with your engine's parts diagram to ensure compatibility.

Q: How often should I perform this maintenance service?
A: Mercury recommends annual maintenance or every 100 hours of operation, whichever comes first. If you operate in sandy, silty, or saltwater conditions, consider more frequent servicing (every 50 hours).

Q: What are the signs that my water pump impeller needs replacement?
A: Common symptoms include weak water stream from the tell-tale, engine overheating, steam from the engine, or reduced cooling system performance. If the impeller blades are cracked, worn, or missing pieces, immediate replacement is required.

Q: Can I reuse the old gaskets if they look okay?
A: No, always replace all gaskets and seals during maintenance even if they appear intact. Reusing old gaskets can lead to leaks, overheating, and premature component failure.

Q: Do I need any special tools to complete this maintenance?
A: Basic hand tools are required including socket sets, screwdrivers, and a torque wrench. The kit includes a gear oil pump (24OP149) for lower unit service, eliminating the need to purchase one separately.

Q: What's the difference between OEM and aftermarket maintenance kits?
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.