300 Hour Maintenance Service Kit – Fits Mercury 40-60 HP EFI FourStroke
300 Hour Maintenance Service Kit – Fits Mercury 40-60 HP EFI FourStroke is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This 300 Hour Maintenance Service Kit – Fits Mercury 40-60 HP EFI FourStroke (Replaces 8M0090559, 8M0113483) provides all the essential components for performing a scheduled 300-hour service on Mercury Marine 40, 50, and 60 HP 4-Stroke EFI outboards from 2000 to the present. Kit selection is critical and depends on whether your outboard has a standard or BigFoot/Command Thrust gearcase.
It serves as a direct replacement for Mercury part numbers 8M0090559 (for BigFoot/CT models) and 8M0113483 (for standard gearcase models), and also contains all components found in the smaller 100-hour service kit (8M0232733).
- Direct Installation: All components are designed for a direct, OEM-compliant fit.
- Gearcase Specific: Kits are configured with the correct anodes and seals for either Standard or BigFoot/Command Thrust gearcases.
- Comprehensive Service: Includes filters, spark plugs, water pump kit, thermostat, and anodes for a complete 300-hour maintenance interval.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury | 8M0090559 | For BigFoot or CommandThrust gearcases |
| Mercury | 8M0113483 | For Standard gearcases |
| Mercury | 8M0232733 | 100-hour kit (subset of components) |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Fitment is for Mercury Marine 4-Cylinder EFI models as specified. Please check your serial number range and gearcase type carefully before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 4-Cylinder EFI | 40 | 4-Stroke | 2000–present | 8M0113483 | Standard gearcase only, Serial numbers 1C453840 & up |
| Mercury | 4-Cylinder EFI | 50 | 4-Stroke | 2000–present | 8M0113483 | Standard gearcase only, Serial numbers 1C453840 & up |
| Mercury | 4-Cylinder EFI | 60 | 4-Stroke | 2000–present | 8M0113483 | Standard gearcase only, Serial numbers 1C453840 & up |
| Mercury | 4-Cylinder EFI BigFoot/CT | 40 | 4-Stroke | 2000–present | 8M0090559 | BigFoot or CommandThrust gearcases only, Serial numbers 1C000001 & up |
| Mercury | 4-Cylinder EFI BigFoot/CT | 50 | 4-Stroke | 2000–present | 8M0090559 | BigFoot or CommandThrust gearcases only, Serial numbers 1C000001 & up |
| Mercury | 4-Cylinder EFI BigFoot/CT | 60 | 4-Stroke | 2000–present | 8M0090559 | BigFoot or CommandThrust gearcases only, Serial numbers 1C000001 & up |
Technical Specs
- Product Type
- 300 Hour Maintenance Service Kit
- Installation
- Direct replacement
- Fuel Type
- Gasoline
- Connection
- OEM Direct Fit
- Housing Color
- Multiple components
- Dimensions (Box)
- Height: 17.5; Width: 22.5; Length: 33.0;
- Fitting Type
- OEM
- Thread Size
- Multiple components
- Warranty
- 1 year factory warranty against defects and workmanship
- Other Technical Attributes
- Available in different configurations based on gearcase type
What’s in the Box
For Standard Gearcase Kit (Replaces 8M0113483):
- 1 x Oil Filter
- 1 x Low Pressure Fuel Filter
- 1 x High Pressure Fuel Filter
- 1 x Oil Drain Seal
- 2 x Gearcase Drain Seals
- 1 x Thermostat
- 2 x Thermostat Gaskets
- 4 x Spark Plugs
- 1 x Water Pump Impeller Kit
- 1 x Power Trim Anode
- 1 x Lower Unit (Gear Case) Anode
For BigFoot/CommandThrust Kit (Replaces 8M0090559):
- 1 x Oil Filter
- 1 x Low Pressure Fuel Filter
- 1 x High Pressure Fuel Filter
- 1 x Thermostat
- 2 x Thermostat Gaskets
- 4 x Spark Plugs
- 1 x Water Pump Impeller Kit
- 1 x Power Trim Anode
- 1 x Lower Unit Anode
- 2 x Gear Case Drain Seals
- 2 x Oil Drain Seals
Installation Notes
- Disconnect the battery and ensure the engine is tilted down to a vertical position.
- Drain the engine oil and gearcase lube into appropriate containers for disposal.
- Replace the oil filter, low-pressure fuel filter, and high-pressure fuel filter.
- Replace the spark plugs, ensuring they are gapped correctly per your engine's specification.
- Disassemble the lower unit to access and replace the water pump impeller and related components from the kit.
- Replace the anostat and its associated gaskets.
- Replace the power trim and lower unit anodes.
- Install new drain seals and refill the engine with the correct specification of oil and gearcase lube.
- Reconnect the battery, start the engine in a safe manner (with water supply), and check for any leaks and proper water pump operation.
- Always dispose of used fluids and old parts according to local regulations.
Troubleshooting & FAQ
How do I choose the correct kit for my 40-60 HP Mercury engine?
The correct kit depends entirely on your outboard's gearcase. Select the kit for the "Standard" gearcase (replaces 8M0113483) or the kit for the "BigFoot" or "Command Thrust (CT)" gearcase (replaces 8M0090559). Check your engine's documentation or the decals on the unit if you are unsure.
What is the difference between this 300-hour kit and the 100-hour kit (8M0232733)?
This 300-hour kit is more comprehensive. It includes everything in the 100-hour kit (oil filter, fuel filters, spark plugs, drain seals) plus additional items required for the extended service interval, such as the water pump impeller kit, anostat and gaskets, and all necessary anodes.
My engine's serial number is close to the listed range. Will this kit fit?
The provided serial number ranges (e.g., 1C453840 & up) are the best guide for compatibility. If your number is outside this range, or if you see conflicting information, we recommend verifying the part numbers in your engine's official service manual before purchasing.
What are the signs that I need to perform this service?
This kit is for scheduled preventative maintenance every 300 operating hours or as specified by Mercury. Signs of a failing component include engine overheating (bad impeller/anostat), poor fuel delivery (clogged filters), or rough running (old spark plugs). Rapidly corroding anodes also indicate they need replacement.
Is this an OEM part?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility. All parts are batch-inspected for quality and consistency.
How fast is shipping?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free for most orders, with expedited options available at checkout where applicable.
What is the warranty and return policy?
This kit is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their 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.
Payment & Security
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