Aftermarket Fuel Pump Assembly for Tohatsu/Nissan 4–9.8 HP and Mercury/Mariner 4–6 HP 4-Stroke Outboards
Aftermarket Fuel Pump Assembly for Tohatsu/Nissan 4–9.8 HP and Mercury/Mariner 4–6 HP 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Aftermarket Fuel Pump Assembly for Tohatsu/Nissan 4–9.8 HP and Merc...
Aftermarket Fuel Pump Assembly for Tohatsu/Nissan 4–9.8 HP and Mercury/Mariner 4–6 HP 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket fuel pump assembly is intended as a replacement for selected 4-stroke outboard applications using the listed Tohatsu, Nissan, Mercury, or Mariner fuel-pump references. It is designed to restore fuel delivery when the original pump is leaking, damaged, or no longer operating correctly.
Applicable manufacturer reference numbers include Tohatsu 3H6-04000-7 and Mercury 803529T06. Always compare the original pump, connection layout, engine model, and manufacturer part number before ordering.
- Aftermarket replacement fuel pump assembly.
- Two hose-barb connections for the fuel inlet and outlet.
- Intended for gasoline 4-stroke outboard applications listed below.
- Installation should be completed with the fuel system depressurized and checked for leaks before operation.
Part Number References
The following numbers are listed as manufacturer replacement or superseded references. Confirm the complete engine application before installation.
| Brand | Reference Number | Reference Status |
|---|---|---|
| Tohatsu | 3H6-04000-7 | Replacement reference |
| Tohatsu | 3H6-04000-0 through 3H6-04000-6 | Earlier reference numbers listed with the 3H6-04000-7 replacement series |
| Mercury | 803529T06 | Replacement reference |
| Mercury | 803529T1, 803529T02, 803529T03 | Earlier reference numbers listed with the 803529T06 replacement series |
Engine and Model Compatibility
The application information below is provided for cross-reference. Engine model, year, serial range, and fuel-system configuration can affect fitment. Match your original part number and inspect the original pump before purchase.
| Brand | Model | Rated HP | Stroke | Reference Number |
|---|---|---|---|---|
| Tohatsu | MFS4A2 | 4 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS4B | 4 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS5A2 | 5 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS5B | 5 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS6A2 | 6 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS6B | 6 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS8A, MFS8A2, MFS8A3 | 8 | 4-Stroke | 3H6-04000-7 |
| Tohatsu | MFS9.8A, MFS9.8A2, MFS9.8A3 | 9.8 | 4-Stroke | 3H6-04000-7 |
| Nissan | NSF4A2 | 4 | 4-Stroke | 3H6-04000-7 |
| Nissan | NSF5A2 | 5 | 4-Stroke | 3H6-04000-7 |
| Nissan | NSF6A2 | 6 | 4-Stroke | 3H6-04000-7 |
| Nissan | NSF8A | 8 | 4-Stroke | 3H6-04000-7 |
| Nissan | NSF9.8A | 9.8 | 4-Stroke | 3H6-04000-7 |
| Mercury / Mariner | Model-specific 4–6 HP applications using the listed reference | 4, 5, or 6 | 4-Stroke | 803529T06 |
Technical Specifications
- Product Type
- Fuel pump assembly
- Part Type
- Aftermarket replacement component
- Fuel Type
- Gasoline
- Connection
- Two hose-barb connections for inlet and outlet lines
- Primary Reference Numbers
- Tohatsu 3H6-04000-7; Mercury 803529T06
- Application
- Selected 4-stroke outboard engines listed on this page
What's in the Box
- 1 × Fuel pump assembly
Gaskets, seals, mounting hardware, hoses, clamps, and other accessories are not included unless specifically shown or listed with the product.
Installation Notes
- Read the engine service information and work in a well-ventilated area away from ignition sources.
- Stop the engine, disconnect the battery where applicable, and relieve fuel-system pressure.
- Place an absorbent cloth beneath the pump and disconnect the inlet and outlet fuel lines. Mark their orientation before removal.
- Remove the original pump and inspect the mounting surface, fuel lines, clamps, and sealing surfaces.
- Install the replacement pump in the same orientation as the original and tighten fasteners according to the engine manufacturer's specifications.
- Reconnect the fuel lines to the correct inlet and outlet ports and secure all clamps.
- Prime the fuel system according to the engine manual.
- Inspect carefully for fuel leaks before starting the engine and again after it reaches operating temperature.
Troubleshooting and FAQ
How can I identify a failing fuel pump?
Possible symptoms include hard starting, hesitation, sputtering, stalling, surging, or loss of power. These symptoms can also result from clogged filters, restricted fuel lines, carburetor problems, air leaks, or ignition faults, so diagnose the complete fuel system before replacing the pump.
Is this pump a direct fit for my engine?
It is intended for the applications and reference numbers listed on this page. Confirm the engine model, horsepower, stroke, serial or year range where applicable, original pump configuration, and manufacturer part number before ordering. Do not rely on horsepower alone.
Does the package include a gasket or new hardware?
No. The package includes one fuel pump assembly only. Gaskets, seals, mounting hardware, hoses, and clamps are not included unless explicitly listed.
Is this an OEM part?
No. This is an aftermarket replacement component. The manufacturer reference numbers are provided for application cross-reference and do not indicate that this product was manufactured by Tohatsu, Nissan, Mercury, or Mariner.
What is the replacement interval?
There is no universal replacement interval for an outboard fuel pump. Inspect it during routine service and replace it when it leaks, shows physical damage, fails testing, or causes verified fuel-delivery problems.
Safety and Important Information
- Fuel is flammable. Keep the work area ventilated and away from sparks, flames, and hot surfaces.
- Verify the original pump's shape, port arrangement, mounting pattern, and reference number before purchase.
- Do not operate the engine if fuel leakage is present.
- Professional installation is recommended when the correct application or fuel-system procedure is uncertain.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for servicing compatible marine engines.
- Application-Focused Listings — Reference numbers and model information are provided to support fitment checks.
- Support Before Installation — Compare the original component and consult the engine service information before fitting a replacement.
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