Fuel Pump Assembly for Tohatsu/Nissan 9.9–30 HP 4-Stroke Outboards – Replaces Tohatsu 3H8-04000-1 and Mercury 803529T04
Fuel Pump Assembly for Tohatsu/Nissan 9.9–30 HP 4-Stroke Outboards – Replaces Tohatsu 3H8-04000-1 and Mercury 803529T04 is backordered and will ship as soon as it is back in stock.
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Fuel Pump Assembly for Tohatsu/Nissan 9.9–30 HP 4-Stroke Outboards ...
Fuel Pump Assembly for Tohatsu/Nissan 9.9–30 HP 4-Stroke Outboards – Replaces Tohatsu 3H8-04000-1 and Mercury 803529T04 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket fuel pump assembly is listed as a replacement for selected Tohatsu and Nissan 4-stroke outboard applications in the 9.9 HP through 30 HP range. It is also listed as a replacement reference for certain Mercury applications using the equivalent fuel-pump specification. Confirm the part number, engine model, year, and original pump configuration before ordering.
The listed replacement references include Tohatsu 3H8-04000-1, 3H8040001, and 3H8040001M, together with Mercury 803529T04 and 5041064. These references are provided for identification and compatibility checking; always compare the original component and connection layout before installation.
- Aftermarket replacement fuel pump assembly for selected outboard applications.
- Designed for the Tohatsu and Nissan MFS/NSF model families listed below.
- Package includes the fuel pump assembly, hose clamps, and O-ring shown in the package contents section.
- Verify the original part number and physical configuration before purchase or installation.
Part Number Matrix
Use the following references to help compare the replacement with your original fuel pump.
| Brand | Replacement Reference |
|---|---|
| Tohatsu | 3H8-04000-1 |
| Tohatsu | 3H8040001 |
| Tohatsu | 3H8040001M |
| Mercury | 803529T04 |
| Mercury | 5041064 |
Engine and Model Compatibility
The listing identifies this fuel pump for selected Tohatsu and Nissan MFS/NSF 4-stroke outboards from 9.9 HP to 30 HP. Model-family references are shown below as an ordering guide. Compatibility can vary by model year, revision, serial-number range, and fuel-system configuration, so confirm the original pump reference before installation.
| Brand | Model Family or Listed Model | Rated HP | Stroke | Listed Reference | Fitment Note |
|---|---|---|---|---|---|
| Tohatsu | MFS 9.9B2, MFS 9.9C | 9.9 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Tohatsu | MFS 15B2, MFS 15C | 15 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Tohatsu | MFS 18B2, MFS 18C | 18 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Tohatsu | MFS 20 | 20 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Tohatsu | MFS 25 | 25 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Tohatsu | MFS 30 | 30 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 9.9B2, NSF 9.9C | 9.9 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 15B2, NSF 15C | 15 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 18B2, NSF 18C | 18 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 20 | 20 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 25 | 25 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Nissan | NSF 30 | 30 | 4-Stroke | 3H8-04000-1 | Verify model year and original pump. |
| Mercury | Specific model not identified in the listing | Not specified | 4-Stroke | 803529T04 | Use the reference number and original pump configuration to confirm fitment. |
Technical Specifications
- Product Type
- Fuel pump assembly
- Application
- Selected Tohatsu/Nissan 9.9–30 HP 4-stroke outboards and certain cross-referenced Mercury applications
- Installation
- Replacement installation; confirm mounting and hose connections before fitting
- Fuel
- For use with the engine manufacturer's specified gasoline and fuel-system requirements
- Housing Color
- Black
- Approximate Weight
- 251 g (0.55 lb)
- Included Service Items
- Hose clamps and O-ring as listed in the package contents
- Product Status
- Aftermarket replacement, not an original equipment manufacturer component
What's in the Box
- 1 x Fuel pump assembly
- 2 x Hose clamp, reference 8M0129429, approximately 9 x 1 mm
- 1 x O-ring, reference 16109003, approximately 3 x 30 mm outside diameter
Installation Notes
- Work safely: Work in a well-ventilated area away from flames, sparks, and other ignition sources. Follow the engine manufacturer's service instructions.
- Prepare the engine: Stop the engine, allow it to cool, disconnect the battery where applicable, and close or isolate the fuel supply before starting work.
- Relieve fuel pressure: If the system is pressurized, relieve pressure carefully and use absorbent cloths or a suitable container to catch residual fuel.
- Disconnect the old pump: Label the fuel and vacuum hoses, if present, before removing them. Prevent dirt from entering the open fuel lines.
- Remove the old assembly: Unbolt the existing pump and clean the mounting area without allowing debris to enter the engine or fuel system.
- Install the replacement: Fit the supplied O-ring or sealing component where applicable. Mount the replacement pump and tighten fasteners to the engine manufacturer's specified torque.
- Reconnect the lines: Reconnect each hose to the correct port and secure the connections with the supplied clamps where appropriate. Do not kink or stretch the hoses.
- Check for leaks: Prime the fuel system according to the engine's procedure. Before operating the boat, inspect the pump and all connections for leaks and correct any problem immediately.
Troubleshooting and FAQ
How do I know if my fuel pump may be failing?
Possible symptoms include difficult starting, poor acceleration, hesitation, stalling, loss of power, or fuel leakage around the pump. These symptoms can also result from restricted fuel lines, a blocked filter, contaminated fuel, ignition faults, or other engine problems. Test the system before replacing parts.
Will this fit my specific engine year?
Year and serial-number coverage is not specified for every model in this listing. Confirm the complete engine model, year, serial number where applicable, original pump appearance, hose routing, and one of the listed reference numbers before ordering.
Can I use this on a Mercury or Mariner outboard?
The listing includes Mercury replacement references 803529T04 and 5041064, but no complete Mercury model list is provided. Do not rely on horsepower alone; verify the exact reference and physical configuration for your engine.
What commonly contributes to fuel-pump problems?
Contaminated fuel, water, debris, deteriorated hoses, restricted filters, and long-term storage with untreated fuel can contribute to fuel-system problems. Diagnose the complete fuel system rather than assuming the pump is the only cause.
Is special maintenance required?
Follow the outboard manufacturer's fuel-system maintenance schedule. Use clean fuel, maintain the fuel filter and hoses, and inspect for leaks or deterioration during routine service.
Is this an OEM part?
No. This listing is for an aftermarket replacement fuel pump assembly. The OEM and manufacturer reference numbers are provided only to assist with identification and fitment checking.
What should I do if the part does not match?
Do not force installation if the mounting points, hose ports, dimensions, or original reference do not match. Stop and verify the application before operating the engine.
Safety and Important Information
- Fuel is flammable. Work only in a ventilated area away from ignition sources.
- Verify the engine model, year, serial-number range where applicable, original part number, and physical configuration before ordering.
- Do not operate the engine if any fuel connection leaks.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended when you are not familiar with outboard fuel systems.
About Sea Sierra
- Marine Replacement Parts — Parts are selected for common marine repair and replacement applications.
- Fitment Support — Compare the original component and reference number before ordering.
- Service-Oriented Assistance — Contact support if you need help checking the listed application details.
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