Fuel Pump Diaphragm Repair Kit for Mercury Mariner 70–90 HP 3-Cylinder and 115 HP 4-Cylinder Outboards
Fuel Pump Diaphragm Repair Kit for Mercury Mariner 70–90 HP 3-Cylinder and 115 HP 4-Cylinder Outboards is backordered and will ship as soon as it is back in stock.
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Fuel Pump Diaphragm Repair Kit for Mercury Mariner 70–90 HP 3-Cylin...
Fuel Pump Diaphragm Repair Kit for Mercury Mariner 70–90 HP 3-Cylinder and 115 HP 4-Cylinder Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This Fuel Pump Diaphragm Repair Kit is designed for 4-stroke Mercury Mariner outboard fuel pumps used on 3-cylinder 70 HP, 75 HP, 80 HP, and 90 HP engines, as well as 4-cylinder 115 HP engines.
It is listed as a replacement for Mercury Marine part numbers 42909A1, 42909A2, 42909A3, and 42909A4. Cross-reference numbers include Sierra 18-7818-1, Mallory 9-37754, and GLM 40280.
- Repair-kit solution for restoring fuel-pump diaphragm function.
- Intended for gasoline fuel systems on the listed 4-stroke outboard applications.
- Some catalog applications specify use with a 90-degree oil check valve on the fuel-pump cover; compare your existing pump before ordering.
- Confirm engine cylinder count, horsepower, serial-number range, and fuel-pump configuration before installation.
Part Number Matrix
Use the following references to compare the replacement with the original and aftermarket catalog numbers.
| Brand | Part Number |
|---|---|
| Mercury Marine | 42909A1 |
| Mercury Marine | 42909A2 |
| Mercury Marine | 42909A3 |
| Mercury Marine | 42909A4 |
| Sierra | 18-7818-1 |
| Mallory | 9-37754 |
| GLM | 40280 |
Engine & Model Compatibility
The company fitment record identifies the following Mercury Mariner outboard applications. Engine serial-number ranges and fuel-pump configurations can vary, so verify the complete engine identification before purchase.
| Brand | Engine Configuration | Rated HP | Stroke | Reference | Notes |
|---|---|---|---|---|---|
| Mercury Mariner | 3-cylinder outboard | 70 HP | 4-stroke | 42909A1–42909A4 | Verify the fuel-pump design and serial-number range. |
| Mercury Mariner | 3-cylinder outboard | 75 HP | 4-stroke | 42909A1–42909A4 | Some catalog applications use a 90-degree oil check valve on the pump cover. |
| Mercury Mariner | 3-cylinder outboard | 80 HP | 4-stroke | 42909A1–42909A4 | Verify the fuel-pump design and serial-number range. |
| Mercury Mariner | 3-cylinder outboard | 90 HP | 4-stroke | 42909A1–42909A4 | Some catalog applications use a 90-degree oil check valve on the pump cover. |
| Mercury Mariner | 4-cylinder outboard | 115 HP | 4-stroke | 42909A1–42909A4 | Confirm the pump body, cover configuration, and serial-number range. |
Technical Specifications
- Product Type
- Fuel pump diaphragm repair kit
- Application
- Mercury Mariner 4-stroke outboard fuel pumps
- Compatible Engine Ratings
- 70 HP, 75 HP, 80 HP, 90 HP, and 115 HP
- Engine Configurations
- 3-cylinder applications from 70–90 HP and 4-cylinder 115 HP applications
- Fuel Type
- Gasoline
- Installation
- Replacement service part; match the original pump configuration before installation
What’s in the Box
- Fuel pump diaphragm repair components for the listed applications
- Gasket component(s) as supplied with the repair kit
Package configuration may vary by production batch. Compare the supplied components with the removed parts and the original fuel-pump assembly before installation.
Installation Notes
Work in a well-ventilated area away from sparks, flames, and other ignition sources. Disconnect the battery and relieve fuel-system pressure before servicing the pump. Clean the pump housing and cover surfaces thoroughly, removing old gasket material and debris. Install the diaphragm and gasket components in the same orientation as the original parts, then tighten fasteners evenly according to the engine manufacturer’s service instructions. After reassembly, prime the fuel system and inspect all connections for leaks before starting or operating the engine.
Troubleshooting & FAQ
How do I know if the fuel pump diaphragm needs replacement?
Possible symptoms include hard starting, stalling, sputtering, loss of power, inconsistent fuel delivery, or fuel leakage around the pump. Diagnose the complete fuel system before replacing the diaphragm.
Which engines does this repair kit fit?
The listed company application covers Mercury Mariner 3-cylinder 70 HP, 75 HP, 80 HP, and 90 HP outboards, plus 4-cylinder 115 HP outboards. Confirm the engine’s stroke, cylinder count, serial-number range, and fuel-pump configuration before ordering.
Does this fit a 100 HP engine?
The current application record does not list a 100 HP engine. Do not assume compatibility based only on horsepower or a similar-looking fuel pump.
What original part numbers does it replace?
This replacement is listed for Mercury Marine 42909A1, 42909A2, 42909A3, and 42909A4. It is also cross-referenced with Sierra 18-7818-1, Mallory 9-37754, and GLM 40280.
Is this an OEM Mercury Marine part?
No. This is an aftermarket replacement repair kit intended for the listed applications. Mercury Marine part numbers are provided only as reference numbers for compatibility identification.
Do all applications use the same fuel-pump configuration?
No. Catalog records identify configuration differences, including applications using a 90-degree oil check valve on the pump cover. Compare the existing pump, cover, and serial-number information before installation.
Safety & Important Information
- Verify the engine model, stroke, cylinder count, horsepower, serial-number range, and fuel-pump configuration before purchase.
- Do not use the part if the supplied components do not match the original pump assembly.
- Fuel-system work can create fire and personal-injury hazards. Follow the engine manufacturer’s service procedures and use qualified professional help when appropriate.
- This is an aftermarket replacement part and is not manufactured by Mercury Marine, Sierra, Mallory, or GLM.
About Sea Sierra
- Marine Replacement Parts — We provide replacement components for common marine service and repair applications.
- Application-Focused Cataloging — Product references and fitment details are organized to help you compare the original part and engine configuration.
- Practical Repair Solutions — Our replacement parts support routine maintenance and repair of marine systems.
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