Mechanical Fuel Pump – Fits MerCruiser V8 454/502 CID (7.4L/8.2L) (Replaces 861677T)
Mechanical Fuel Pump – Fits MerCruiser V8 454/502 CID (7.4L/8.2L) (Replaces 861677T) is backordered and will ship as soon as it is back in stock.
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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.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Mechanical Fuel Pump – Fits MerCruiser V8 454/502 CID (7.4L/8.2L) (...
Product Details
This is an aftermarket Mechanical Fuel Pump – Fits MerCruiser V8 454/502 CID (7.4L/8.2L) (Replaces 861677T), designed for V-8 MerCruiser stern drive and inboard engines with 454 and 502 CID (7.4L and 8.2L) GM blocks. It is engineered for applications using a sea water pump with a mounted mechanical fuel pump.
It serves as a direct replacement for Mercury/Quicksilver part numbers 861677T, 818383T, and Sierra 18-8860.
- Installation: Mounts directly onto the sea-pump assembly.
- Fuel System: Designed for gasoline-fueled engines.
- Package Includes: Comes with the required mounting gasket for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury / Quicksilver | 861677T |
| Mercury / Quicksilver | 818383T |
| Sierra | 18-8860 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This fuel pump is compatible with specific General Motors big block engines used by MerCruiser. Verify your model and original part number before ordering.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| MerCruiser | V8 454 CID | 330-385 | 4-Stroke | 861677T | GM Big Block |
| MerCruiser | V8 502 CID | 415-425 | 4-Stroke | 861677T | GM Big Block |
| MerCruiser | 7.4L | 330-385 | 4-Stroke | 861677T | GM Big Block |
| MerCruiser | 8.2L | 415-425 | 4-Stroke | 861677T | GM Big Block |
Technical Specs
- Product Type
- Mechanical Fuel Pump
- Installation
- Sea-pump mounted
- Fuel Type
- Gasoline
- Connection Orientation
- Inlet at 9 o'clock, Outlet at 6 o'clock
- Housing Material
- Metal
- Housing Color
- Silver/Chrome
- Dimensions
- L: 165mm × W: 120mm × H: 120mm
- Weight
- 0.79 kg (1.74 lbs)
- Fitting Type
- Flange Mount
- Other Attributes
- For use on sea water pumps with mechanical fuel pump mounted applications
- Warranty
- 1 year factory warranty against defects and workmanship
What’s in the Box
- 1 x Fuel Pump Assembly (861677T)
- 1 x Gasket (27-34213)
Installation Notes
- Disconnect the battery and relieve any pressure from the fuel system.
- Place absorbent rags under the fuel lines to catch any spills.
- Carefully disconnect the inlet and outlet fuel lines from the pump.
- Remove the mounting bolts that secure the old fuel pump to the engine block or sea-pump.
- Remove the old pump and gasket. Thoroughly clean the mounting surface to ensure a proper seal.
- Place the new gasket onto the mounting surface.
- Install the new fuel pump and tighten the mounting bolts to the manufacturer's recommended torque.
- Reconnect the fuel lines securely.
- Reconnect the battery, prime the fuel system, and start the engine. Check carefully for any fuel leaks.
Troubleshooting & FAQ
How do I know if this fuel pump fits my MerCruiser engine?
This pump is designed for MerCruiser V8 454/502 CID (7.4L/8.2L) GM engines where the mechanical fuel pump is mounted on the sea water pump. The best way to confirm fitment is to match your original part number to the ones listed: 861677T, 818383T, or Sierra 18-8860. Also, check the connection orientation (inlet at 9 o'clock, outlet at 6 o'clock).
What are the common signs of a failing mechanical fuel pump?
Symptoms of a bad fuel pump include engine sputtering at high speeds, loss of power, difficulty starting, or engine stalling. You might also notice fuel leaking from the pump housing, which is a serious safety hazard and requires immediate attention.
How often should a mechanical fuel pump be replaced?
There is no fixed replacement interval for mechanical fuel pumps. They are typically replaced when they fail or show signs of wear. Regular inspection for leaks and performing fuel pressure tests during routine maintenance can help identify a weakening pump before it fails completely.
Is this a difficult part to install?
For someone with intermediate mechanical skill, the replacement is straightforward. It requires basic hand tools, care in handling fuel lines, and ensuring the mounting surface is clean for a good seal. However, due to the fire risk associated with fuel systems, professional installation is always recommended if you are not completely comfortable with the process.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility and batch-inspected for consistency and reliability.
Shipping speed & cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, and expedited options may be available at checkout depending on your location.
Warranty & returns?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not order.
- This is an aftermarket replacement component, not an OEM part.
- 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 quality control.
Payment & Security
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