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Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4)
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Fuel Pump Diaphragm Kit – Fits Mercury Mariner 70-115 HP (Replaces 42909A1, 42909A2, 42909A3, 42909A4)
This fuel pump diaphragm kit fits select Mercury and Mariner 2-Stroke outboards, including 70-90 HP 3-cylinder models (1983–1993) and 100-115 HP 4-cylinder models (1988–1993). It allows for a complete rebuild of the fuel pump assembly.
This kit is a direct replacement for Mercury OEM part numbers 42909A1, 42909A2, 42909A3, and 42909A4. It also cross-references with Sierra 18-7818-1, Mallory 9-37754, and GLM 40280.
- Product Type: Fuel Pump Diaphragm Rebuild Kit
- Installation: Direct replacement for original components
- Package Contents: Includes gaskets and diaphragms for a complete rebuild
Part Number Cross-Reference
Use this table to confirm equivalent part numbers across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercury | 42909A1 |
| Mercury | 42909A2 |
| Mercury | 42909A3 |
| Mercury | 42909A4 |
| Sierra | 18-7818-1 |
| Mallory | 9-37754 |
| GLM | 40280 |
Compatible Engine Models
Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 3-cylinder | 70 | 2-Stroke | 1983–1990 | 42909A1 | |
| Mercury | 3-cylinder | 75 | 2-Stroke | 1987–1993 | 42909A1 | Models with 90-degree oil check valve on pump cover |
| Mercury | 3-cylinder | 80 | 2-Stroke | 1987–1990 | 42909A1 | |
| Mercury | 3-cylinder | 90 | 2-Stroke | 1987–1993 | 42909A1 | Models with 90-degree oil check valve on pump cover |
| Mercury | 4-cylinder | 100 | 2-Stroke | 1988–1993 | 42909A3 | Models with 90-degree oil check valve on pump cover/white fuel pump body |
| Mercury | 4-cylinder | 115 | 2-Stroke | 1988–1993 | 42909A3 | Models with white fuel pump body |
Technical Specifications
| Specification | Value |
|---|---|
| Product Type | Fuel Pump Diaphragm Kit |
| Installation | Direct replacement |
| Fuel Type | Gasoline |
| Connection | N/A - Internal component |
| Fitting Type | N/A - Internal component |
| Thread Size | N/A |
| Warranty | 1 year (manufacturer defects) |
| Other Technical Attributes | Compatible with 90-degree oil check valve models |
Package Contents
- 1 x Fuel Pump Diaphragm Kit (includes gaskets and diaphragms for a complete rebuild)
Installation Guide
- Disconnect the battery and relieve any pressure in the fuel system before starting.
- Remove the fuel pump from the engine assembly, carefully noting the orientation of fuel lines and fittings.
- Disassemble the pump on a clean workbench, paying close attention to the order and orientation of diaphragms, gaskets, and covers.
- Thoroughly clean all housing surfaces to remove any old gasket material or debris.
- Inspect the pump housing for cracks, warping, or other damage before proceeding.
- Install the new diaphragms and gaskets from the kit, ensuring they align correctly with the housing passages.
- Reassemble the pump housing, tightening screws in a crisscross pattern to ensure an even seal and prevent leaks.
- Mount the rebuilt fuel pump back onto the engine and securely reconnect all fuel lines.
- Prime the fuel system according to the manufacturer's procedure and carefully check for any fuel leaks before starting the engine.
Troubleshooting & FAQ
How do I confirm this diaphragm kit fits my engine?
This kit is designed for specific Mercury/Mariner 3-cylinder (70-90 HP, 1983–1993) and 4-cylinder (100-115 HP, 1988–1993) models. Always cross-reference your engine's OEM part number with the numbers listed in our compatibility tables. Pay close attention to notes, as some models are only compatible if they have a 90-degree oil check valve or a specific (white) fuel pump body.
What are the signs of a failing fuel pump diaphragm?
Common signs include the engine bogging down at high speeds, difficulty starting, rough idling, or visible fuel leaks around the pump housing. A ruptured diaphragm can also allow fuel to leak into the engine crankcase, which can cause significant damage.
Is this kit all I need for a complete fuel pump rebuild?
Yes, this kit includes the essential gaskets and diaphragms required for a standard rebuild of the fuel pump. We recommend reviewing the product images to visually confirm all the components you require are included.
OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.
How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.
What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.
Important Notes
- Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
- This product is an aftermarket replacement part and is not an OEM component.
- Professional installation is recommended to ensure safety and optimal performance.
Why Choose JLM MARINE?
- Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
- Fast Global Shipping: Free delivery worldwide in 5–15 days.
- Direct from Manufacturer: Competitive pricing without compromising quality.
We can ship to virtually any address in the world with free shipping available for most regions.
For our typical US and Canadian customers , our shipping timeframes are as follows:
- Amazon FBA: orders will be delivered within 1-5 business days after placing the order (during certain special periods such as major promotions, Christmas, etc., the delivery time of Amazon FBA may be affected).
- US warehouse shipment: orders will be delivered within 5 days after placing the order.
- China warehouse shipment: orders will be delivered about 12 days after placing the order.
When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.
Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.
Founded in 2002, JLM Marine has established itself as a dedicated manufacturer of high-quality marine parts, based in China. Our commitment to excellence in manufacturing has earned us the trust of top marine brands globally.
As a direct supplier, we bypass intermediaries, which allows us to offer competitive prices without compromising on quality. This approach not only supports cost-efficiency but also ensures that our customers receive the best value directly from the source.
We are excited to expand our reach through retail channels, bringing our expertise and commitment to quality directly to boat owners and enthusiasts worldwide.
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