Fuel Pump Diaphragm Gasket Kit – Fits Mercury/Mariner Outboard (Replaces Mercury Marine 89031A1)
Fuel Pump Diaphragm Gasket Kit – Fits Mercury/Mariner Outboard (Replaces Mercury Marine 89031A1) 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).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Fuel Pump Diaphragm Gasket Kit – Fits Mercury/Mariner Outboard (Rep...
Product Details
This Fuel Pump Diaphragm Gasket Kit provides the essential components to restore your fuel pump's performance. It is designed for a wide range of Mercury Marine and Mariner outboard engines. For precise fitment, it is recommended to confirm compatibility using your engine's OEM serial number.
This kit serves as a direct replacement for Mercury Marine 89031A1 and 66599A1, as well as aftermarket equivalents like Sierra 18-7811, GLM 40350, and Mallory 9-37756.
- Aftermarket versions include essential O-rings and a fuel filter.
- Restores fuel pump function and prevents leaks.
- Built to meet or exceed original equipment specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury Marine | 89031A1 |
| Mercury Marine | 66599A1 |
| Sierra | 18-7811 |
| GLM | 40350 |
| Mallory | 9-37756 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury engines, it's crucial to verify fitment against your specific serial number, as this kit covers a broad range of outboard models.
For Mariner outboards, please confirm compatibility using your engine's serial number to ensure a correct match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Outboard | 89031A1 | Please confirm fitment with engine serial number. | |||
| Mariner | Outboard | 89031A1 | Please confirm fitment with engine serial number. |
Technical Specs
- Product Type
- Fuel Pump Diaphragm Gasket Kit
- Dimensions
- Length: 1.5 in (38.1 mm) | Width: 6.0 in (152.4 mm) | Height: 7.5 in (190.5 mm)
- Weight
- 0.04 lbs (0.01 kg)
- Warranty
- 1 year factory warranty (OEM) | Limited Lifetime (Sierra aftermarket)
What’s in the Box
- 1 x Fuel Pump Diaphragm Gasket Kit (89031A1/66599A1)
- 1 x O-Ring (18-7411) - Included in Sierra 18-7811 kit
- 1 x O-Ring (18-7120) - Included in Sierra 18-7811 kit
- 1 x Fuel Filter - Included in Sierra 18-7811 kit
Installation Notes
- Disconnect the battery and relieve fuel system pressure to prevent fuel spray.
- Place absorbent rags around the fuel pump to catch any spilled fuel.
- Carefully disconnect the fuel lines and remove the bolts securing the old fuel pump assembly.
- Disassemble the pump and remove the old diaphragm and gaskets. Note their orientation.
- Clean all mating surfaces thoroughly, ensuring they are free of old gasket material and debris.
- Install the new diaphragm and gaskets from the kit, ensuring correct alignment.
- Reassemble the fuel pump and secure it back onto the engine block, tightening bolts to the manufacturer's specified torque.
- Reconnect fuel lines, prime the fuel system, and check for leaks before starting the engine.
Troubleshooting & FAQ
How do I know if this kit fits my engine?
This kit fits a wide variety of Mercury and Mariner outboards. The most reliable method for confirming compatibility is to match your engine's serial number with the OEM part number (89031A1 or 66599A1). Do not rely on model and year alone.
What are the signs of a failing fuel pump diaphragm?
Common symptoms include the engine running rough, stalling, hesitating on acceleration, or a noticeable fuel leak from the pump's weep hole. You may also find fuel mixing with the engine oil.
How often should the fuel pump diaphragm be replaced?
There is no fixed interval, but diaphragms can degrade over time, especially with modern ethanol-blended fuels. It's good practice to inspect it during regular service or replace it every 5-7 years as preventative maintenance.
Is any special tool needed for installation?
Standard mechanical hand tools are generally sufficient. A torque wrench is recommended for tightening the pump bolts to the correct specification to avoid leaks or damage.
What's the difference between the OEM and Sierra aftermarket kit?
The primary difference is that the Sierra aftermarket kit (18-7811) often includes extra components such as O-rings and a fuel filter, providing a more comprehensive service package. The core diaphragm and gaskets are built to the same specifications as the OEM part.
Can I replace just the diaphragm instead of the whole kit?
This product is a kit that includes the diaphragm and necessary gaskets/seals for a complete repair. It is highly recommended to replace all components in the kit to ensure a proper seal and prevent future leaks.
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.
Payment & Security
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