Aftermarket Mechanical Fuel Pump for Mercury 4–6 HP and Tohatsu/Nissan 4–9.8 HP 4-Stroke Outboards — Replaces 803529T01, 803529T02 and 803529T06
Aftermarket Mechanical Fuel Pump for Mercury 4–6 HP and Tohatsu/Nissan 4–9.8 HP 4-Stroke Outboards — Replaces 803529T01, 803529T02 and 803529T06 is backordered and will ship as soon as it is back in stock.
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Aftermarket Mechanical Fuel Pump for Mercury 4–6 HP and Tohatsu/Nis...
Aftermarket Mechanical Fuel Pump for Mercury 4–6 HP and Tohatsu/Nissan 4–9.8 HP 4-Stroke Outboards — Replaces 803529T01, 803529T02 and 803529T06 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket mechanical fuel pump is designed for select 4-stroke Mercury Marine 4–6 HP outboards and Tohatsu/Nissan MFS and NSF 4–9.8 HP outboards. It is actuated by the engine camshaft and is intended to provide dependable fuel delivery when replacing a compatible original pump.
Use the engine model, horsepower, stroke, and existing part number together when confirming fitment. This replacement is associated with Mercury Marine references 803529T, 803529T01, 803529T02, 803529T03, and 803529T06, as well as Tohatsu/Nissan references 3H6-04000-0 through 3H6-04000-7.
- Mechanical pump activated by the engine camshaft.
- Designed for specified small 4-stroke outboard applications.
- Supplied as a replacement pump kit with an O-ring and clamps.
- Verify the original pump, mounting arrangement, connections, and part number before ordering.
Part Number Matrix
The following are manufacturer and cross-reference numbers associated with this replacement application. They are provided for identification and compatibility checking only.
| Brand | Part Number |
|---|---|
| Mercury Marine | 803529T |
| Mercury Marine | 803529T01 |
| Mercury Marine | 803529T02 |
| Mercury Marine | 803529T03 |
| Mercury Marine | 803529T06 |
| Tohatsu / Nissan | 3H6-04000-0 |
| Tohatsu / Nissan | 3H6-04000-1 |
| Tohatsu / Nissan | 3H6-04000-2 |
| Tohatsu / Nissan | 3H6-04000-3 |
| Tohatsu / Nissan | 3H6-04000-4 |
| Tohatsu / Nissan | 3H6-04000-5 |
| Tohatsu / Nissan | 3H6-04000-6 |
| Tohatsu / Nissan | 3H6-04000-7 |
Engine and Model Compatibility
Fitment depends on the complete engine configuration. Confirm the brand, model designation, horsepower, 4-stroke configuration, and existing pump number before installation.
| Brand | Model | Rated HP | Stroke | Associated Part Numbers |
|---|---|---|---|---|
| Mercury | 4 HP Carb | 4 | 4-Stroke | 803529T, 803529T01, 803529T02, 803529T03, 803529T06 |
| Mercury | 5 HP Carb, including 5 HP Carb JCI model | 5 | 4-Stroke | 803529T, 803529T01, 803529T02, 803529T03, 803529T06 |
| Mercury | 6 HP Carb | 6 | 4-Stroke | 803529T, 803529T01, 803529T02, 803529T03, 803529T06 |
| Tohatsu | MFS4A2, MFS4B, MFS4C | 4 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Nissan | NSF4A2, NSF4B, NSF4C | 4 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Tohatsu | MFS5A2, MFS5B, MFS5C | 5 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Nissan | NSF5A2, NSF5B, NSF5C | 5 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Tohatsu | MFS6A2, MFS6B, MFS6C | 6 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Nissan | NSF6A2, NSF6B, NSF6C | 6 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Tohatsu | MFS8A2, MFS8A3 | 8 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Nissan | NSF8A2, NSF8A3 | 8 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Tohatsu | MFS9.8A2, MFS9.8A3 | 9.8 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
| Nissan | NSF9.8A2, NSF9.8A3 | 9.8 | 4-Stroke | 3H6-04000-0 through 3H6-04000-7 |
Technical Specifications
- Product Type
- Marine outboard mechanical fuel pump
- Application
- Select Mercury, Tohatsu, and Nissan 4-stroke outboards listed above
- Fuel Type
- Gasoline
- Actuation
- Mechanical; activated by the engine camshaft
- Connections
- Hose-barb inlet and screw-type outlet connection
- Housing Material
- Metallic marine fuel-pump housing; exact material not specified
- Housing Color
- Silver / metallic
- Dimensions
- 114.5 × 91 × 62 mm (4.53 × 3.58 × 2.44 in), listed package dimensions
- Weight
- 0.18 kg (6.4 oz)
- Fitting Type
- Transom-mount application
- Thread Size
- 0.25 in connection size
What's in the Box
- 1 × fuel pump
- 2 × clamps / clips
- 1 × O-ring
Associated component references include fuel pump reference 803529T01 / 3H6-04000-1, clamps / clips reference 54-95395, and O-ring reference 25-803513. Confirm the supplied components against the product received before installation.
Installation Notes
- Review the engine service information and confirm that the replacement pump matches the original pump and mounting arrangement.
- Disconnect the battery or follow the engine manufacturer's procedure for preventing accidental starting.
- Relieve fuel-system pressure as directed by the engine service information.
- Place absorbent material below the fuel connections to contain spilled fuel.
- Disconnect and identify the fuel inlet and outlet lines before removing the original pump.
- Remove the original pump and clean the mounting surface.
- Install the supplied O-ring and mount the replacement pump in the correct orientation.
- Tighten the mounting fasteners to the engine manufacturer's specified torque.
- Reconnect the fuel lines to the correct ports and secure them with the supplied clamps.
- Prime the fuel system if required for the engine model, then inspect all connections for leaks before operating the engine.
Troubleshooting and FAQ
How do I confirm fitment?
Compare the complete engine model, horsepower, 4-stroke configuration, existing pump, mounting arrangement, and part number with the compatibility information above. Do not rely on horsepower alone.
What symptoms can indicate a failing mechanical fuel pump?
Possible symptoms include hard starting, rough idle, sputtering, hesitation, loss of power, or stalling under load. Fuel-system and ignition checks should be performed before replacing the pump.
Is this an electric or mechanical pump?
This is a mechanical fuel pump actuated by the engine camshaft. It is not described as an electrically powered fuel pump.
What do the T01, T02, and T06 suffixes mean?
Suffixes may identify revisions or superseding versions of a manufacturer's part number. Confirm the exact application and part-number relationship for your engine before ordering.
Is this an OEM part?
This listing is for an aftermarket replacement fuel pump. The manufacturer-branded numbers shown above are reference numbers for identification and compatibility checking; the replacement itself is not represented as an original OEM component.
What should I do if the pump or connections differ from my original?
Do not force installation or modify the fuel system. Compare the part with the original and contact support before use if the mounting, ports, dimensions, or supplied components do not match.
Safety and Important Information
- Work in a well-ventilated area away from flames, sparks, and other ignition sources.
- Allow the engine and fuel system to cool before servicing.
- Use suitable fuel-resistant equipment and dispose of spilled fuel safely.
- Inspect every connection for leaks before starting or operating the engine.
- Professional installation is recommended when the correct fitment or fuel-system procedure is uncertain.
About Sea Sierra
- Marine Replacement Parts — Replacement components for selected marine engine applications.
- Fitment-Focused Listings — Product references and compatibility information are provided to help customers compare their original parts.
- Customer Support — Contact support with your engine model and original part information if you need help checking compatibility.
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