Outboard Maintenance Kit – Fits Mercury/Mariner 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0)
Outboard Maintenance Kit – Fits Mercury/Mariner 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
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Outboard Maintenance Kit – Fits Mercury/Mariner 4-6 HP 4-Stroke (Re...
Outboard Maintenance Kit – Fits Mercury/Mariner 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0) is backordered and will ship as soon as it is back in stock.
Product Details
This Outboard Maintenance Kit – Fits Mercury/Mariner 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0) contains essential components for performing routine 300-hour service on Mercury and Mariner 4HP, 5HP, and 6HP 4-Stroke outboard motors (serial numbers 0R411838 and above).
It serves as a direct aftermarket replacement for Mercury/Mariner part numbers 8M0120836 and 3GR-87500-0.
- Complete kit for scheduled 300-hour outboard service intervals.
- Includes engine-specific replacement components for fuel and cooling systems.
- Engineered for gasoline-fueled 4-stroke marine engines.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/Mariner | 8M0120836 |
| Mercury/Mariner | 3GR-87500-0 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury/Mariner Owners: This kit is designed for specific 4-Stroke models from 4HP to 6HP with serial numbers 0R411838 and newer. Please verify your serial number before ordering.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury/Mariner | 4HP | 4 | 4-Stroke | 8M0120836 | Serial numbers 0R411838 and above |
| Mercury/Mariner | 5HP | 5 | 4-Stroke | 8M0120836 | Serial numbers 0R411838 and above |
| Mercury/Mariner | 6HP | 6 | 4-Stroke | 8M0120836 | Serial numbers 0R411838 and above |
Technical Specs
- Product Type
- Outboard Maintenance Service Kit
- Installation
- Engine-specific replacement components
- Fuel Type
- Gasoline
- Housing Material
- Multiple materials (Neoprene impeller)
- Weight
- 0.045 kg (0.1 lb)
- Other Technical Attributes
- 300-Hour service interval maintenance kit
What’s in the Box
- 1 x Water Pump Impeller (47-16154-3)
- 1 x Cotter Pin (8150264)
- 1 x Pin Key (28-16155)
- 1 x Thermostat (804540)
- 1 x Thermostat Gasket (27-8M0214960)
- 1 x O-Ring (25-16131)
- 1 x Oil Seal (16130/26-16130)
- 1 x Fuel Filter (35-8M0157133)
- 1 x Gaskets (8035161)
- 2 x Drain Gasket (27-95220)
Installation Notes
- Disconnect the battery and fuel lines for safety.
- Position a drain pan and remove the drain plugs to empty the engine oil and gearcase lubricant.
- Disassemble the lower unit to access and replace the water pump impeller, seals, and key.
- Remove the thermostat cover, then install the new thermostat and gasket.
- Locate and replace the existing fuel filter with the new one.
- Install new drain plug gaskets, tighten the plugs to the manufacturer's torque specification, and refill the engine and gearcase with the correct grade of oil.
- Reconnect fuel lines and the battery.
- Before navigating, run the engine and carefully check for any fuel, oil, or water leaks.
Troubleshooting & FAQ
How do I know if this kit fits my engine?
This kit is specifically for Mercury and Mariner 4HP, 5HP, and 6HP 4-stroke outboard motors with serial numbers 0R411838 and newer. Always check your engine's serial number against the compatibility table before purchasing.
What is the recommended service interval for this kit?
This is a 300-hour service kit. It is designed to replace key components as part of your engine's scheduled maintenance routine every 300 hours of operation or as specified by the manufacturer.
What are signs that my outboard needs this maintenance?
Common indicators include engine overheating (often due to a worn impeller), poor fuel flow (clogged filter), or if it has been 300 operating hours since the last major service. Preventative maintenance is key to avoiding failure.
Are special tools required for installation?
Standard mechanic's tools are required. A torque wrench is highly recommended for tightening drain plugs and other components to manufacturer specifications to prevent leaks and damage.
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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