Mercury Outboard Water Pump Impeller 8-Blade - 8M0135803
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The Mercury Quicksilver 8M0135803 is a genuine Mercury Marine OEM water pump impeller used in select Mercury and Mariner portable outboard lower-unit water pump assemblies. The impeller is the flexible-vane component that draws raw water through the gearcase pickup and pumps it up through the cooling system to help regulate engine temperature.
This impeller is commonly associated with select modern Mercury EFI portable outboards and should be matched by exact engine serial number, horsepower, gearcase style, and factory water pump diagram before ordering.
Key Features
- Genuine Mercury Marine OEM water pump impeller.
- Mercury/Quicksilver part number: 8M0135803.
- Mercury category-style formatting: 47-8M0135803.
- UPC / GTIN reference: 745061029514.
- Flexible 8-blade impeller design.
- Used in select portable Mercury outboard water pump assemblies.
- Helps maintain proper cooling-water flow to prevent overheating.
- Important replacement part for annual service, weak telltale flow, overheating, or lower-unit pump rebuilds.
- Supersedes earlier Mercury impeller references in supported applications.
- Cross-reference links exist for select Tohatsu/Nissan applications, but fitment must be confirmed by engine model and parts diagram.
Technical Specifications
- Overall diameter: 41.11 mm / 1.62 in.
- Height / thickness: 23.51 mm / 0.93 in.
- Shaft insertion diameter: 13.88 mm / 0.55 in.
- Blade count: 8 flexible vanes
- Application type: raw-water pump impeller
- Service location: lower-unit water pump assembly
Engine Compatibility
Common application context includes select Mercury, Mariner, Tohatsu, and Nissan portable outboards where the factory water pump diagram calls for 8M0135803, including:
- Select Mercury 15 HP EFI outboards where specified.
- Select Mercury 20 HP EFI outboards where specified.
- Select Mercury / Mariner 10 HP, 15 HP, and 20 HP EFI configurations where the serial-number parts chart confirms this impeller.
- Select Mercury 8 HP and 9.9 HP Command Thrust gearcase applications where specified.
- Select Tohatsu / Nissan MFS9.9, MFS15, MFS18, and MFS20 applications only where the OEM parts chart confirms the matching impeller reference.
Use this impeller only where the Mercury, Mariner, Tohatsu, or Nissan parts diagram specifically calls for 8M0135803, 47-8M0135803, or a confirmed cross-reference.
Serial Number Fitment Notice
Confirm fitment by outboard serial number, horsepower, gearcase style, water pump housing, driveshaft size, and factory parts diagram before ordering. Mercury portable outboards can use different impellers depending on production range, EFI generation, Command Thrust gearcase, and lower-unit configuration.
Common serial-number references should be treated as a guide only. Always verify against the exact serial-number parts lookup before installation.
When This Part Needs Replacement
Replace the impeller during scheduled water pump service or whenever the engine has weak telltale flow, overheating, poor cooling-water output, melted or deformed pump components, cracked vanes, missing blade pieces, or suspected dry-run damage. It should also be replaced after long storage, debris ingestion, sand or silt operation, or any service where the lower-unit water pump is opened.
Installation Notes
Inspect the water pump cup, wear plate, gaskets, key, pump housing, water tube grommet, and driveshaft sealing area before installing the new impeller. Replace damaged or compressed gaskets and seals rather than reusing them.
Lubricate the impeller and pump cup with clean water, soapy water, or the lubricant specified in the service manual during assembly. Install the drive key correctly and rotate the driveshaft in the proper direction while seating the housing so the impeller vanes fold the correct way. After installation, run the outboard on a proper water supply and confirm strong cooling-water flow before returning the engine to service.
Alternate/Superseded Part Numbers
- 8M0135803 — Mercury/Quicksilver OEM impeller part number
- 47-8M0135803 — Mercury category-style catalog formatting
- 745061029514 — UPC / GTIN reference
- 47-803748 — earlier Mercury reference; verify by serial number and diagram
- 47-803748002 — earlier Mercury reference; verify by serial number and diagram
- 47-8M0214944 — related/supersession reference; verify by serial number and diagram
- Tohatsu 334-65021-0 — cross-reference; verify by model and diagram
- Tohatsu 3LD-65021-0 — cross-reference; verify by model and diagram
Related Service Parts
Depending on the pump condition, service may also require the water pump plate, upper pump housing, lower pump gaskets, drive key, water tube grommet, and complete water pump repair kit. Confirm related parts by engine serial number before ordering.
Parts Desk Insight
Impellers should be replaced before they fail. A worn or dry-run impeller can shed vane pieces into the cooling passages and cause overheating even after a new impeller is installed. During service, inspect the full pump stack and confirm the correct gearcase version, especially on EFI and Command Thrust portable models.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
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