Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4)
Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces ...
Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4) is backordered and will ship as soon as it is back in stock.
Product Details
This Fuel Pump Diaphragm Kit is designed for Mercury Mariner 70–115 HP outboard engines, specifically fitting 3-cylinder (70, 75, 80, 90 HP) and 4-cylinder (100, 115 HP) models manufactured between 1983–1993.
It serves as a direct cross-reference for Mercury part numbers 42909A1, 42909A2, 42909A3, and 42909A4, and interchanges with Sierra 18-7818-1, Mallory 9-37754, and GLM 40280.
- Direct replacement fit for straightforward installation.
- Engineered for use with standard gasoline fuel systems.
- Compatible with models equipped with a 90-degree oil check valve on the pump cover.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury | 42909A1 |
| Mercury | 42909A2 |
| Mercury | 42909A3 |
| Mercury | 42909A4 |
| Sierra | 18-7818-1 |
| Mallory | 9-37754 |
| GLM | 40280 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure accurate fitment.
| Brand | Model | Rated HP | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury | 3-cylinder | 70 | 1983–1990 | 42909A1 | |
| Mercury | 3-cylinder | 75 | 1987–1993 | 42909A1 | Models with 90-degree oil check valve on pump cover |
| Mercury | 3-cylinder | 80 | 1987–1990 | 42909A1 | |
| Mercury | 3-cylinder | 90 | 1987–1993 | 42909A1 | Models with 90-degree oil check valve on pump cover |
| Mercury | 4-cylinder | 100 | 1988–1993 | 42909A3 | Models with 90-degree oil check valve on pump cover/white fuel pump body |
| Mercury | 4-cylinder | 115 | 1988–1993 | 42909A3 | Models with white fuel pump body |
Technical Specs
- Product Type
- Fuel Pump Diaphragm Kit
- Installation
- Direct replacement
- Fuel Type
- Gasoline
- Other Technical Attributes
- Compatible with 90-degree oil check valve models
What’s in the Box
- 1 x Diaphragm (replaces 42909A1, 42909A2, 42909A3, 42909A4)
- 1 x Gasket (replaces 987691)
Installation Notes
For a safe and effective installation, disconnect the battery and relieve all fuel system pressure before beginning work. Clean the fuel pump housing and cover surfaces thoroughly to remove any old gasket material or debris. Install the new diaphragm and gasket, ensuring correct orientation. Tighten all fasteners evenly to the manufacturer's recommended torque specifications to prevent leaks. After reassembly, prime the fuel system and carefully inspect for any signs of fuel leakage before starting the engine.
Troubleshooting & FAQ
How do I know if my fuel pump diaphragm is failing?
Common signs of a faulty diaphragm include the engine failing to start, stalling unexpectedly, sputtering or losing power at high speeds, or visible fuel leaks around the fuel pump housing.
Is this kit compatible with my specific engine?
This kit is designed for a specific range of Mercury/Mariner engines from 1983–1993. It is critical to consult the compatibility table and pay close attention to notes regarding the number of cylinders, the presence of a 90-degree oil check valve, or the color of the fuel pump body to ensure a correct match.
What is the difference between the 42909A1, A2, A3, and A4 part numbers?
These numbers typically represent successive revisions or updates from the original equipment manufacturer. This aftermarket diaphragm kit is designed to be a universal replacement that covers all of these superseded part numbers.
When should a fuel pump diaphragm be replaced?
While there is no fixed service interval, it is recommended to inspect the fuel system components annually. You should replace the diaphragm immediately if you notice any signs of wear, brittleness, cracking, or fuel leakage to prevent fuel delivery issues and potential engine damage.
Is this an OEM part?
This is a high-quality aftermarket replacement part, not an OEM component. It is engineered to meet or exceed original equipment specifications for fit, form, and function and is produced in an ISO 9002 certified facility to ensure consistent quality.
How fast is shipping?
We ship worldwide, with most orders arriving in 5–15 days via standard shipping. Standard delivery is free, and expedited options are available at checkout for most regions.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal operating conditions. If you encounter an issue, please contact our support team with your order details. Returns of unused items in their original condition are accepted within our standard return window. Please see our full policy page or contact us for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model is listed as compatible—do not order.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is strongly recommended for safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions with an average transit time of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
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