Heavy Duty Sea Water Pump Impeller Kit – Fits Mercury MerCruiser 4.5L, 6.2L MCM, MIE & TowSport Models (Replaces 47-8M0137221)
Heavy Duty Sea Water Pump Impeller Kit – Fits Mercury MerCruiser 4.5L, 6.2L MCM, MIE & TowSport Models (Replaces 47-8M0137221) 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.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
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Heavy Duty Sea Water Pump Impeller Kit – Fits Mercury MerCruiser 4....
Heavy Duty Sea Water Pump Impeller Kit – Fits Mercury MerCruiser 4.5L, 6.2L MCM, MIE & TowSport Models (Replaces 47-8M0137221) is backordered and will ship as soon as it is back in stock.
Product Details
This Heavy Duty Sea Water Pump Impeller Kit is designed as a direct-fit replacement for specific Mercury MerCruiser engines. It is engineered for late-model MerCruiser 4.5L engines (serial numbers 2A531163 and up) and 6.2L MCM (sterndrive), MIE (inboard), and TowSport models (serial numbers 2A531197+, 2A530774+, and 2A531348+ respectively).
This kit serves as a direct replacement for Mercury/MerCruiser part numbers 47-8M0137221 and the superseded part 98-8M0121940.
- Installs directly in the OEM sea water pump housing.
- Features a robust 8-blade design for efficient water flow.
- Kit includes the impeller, wear plates, and seal for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Mercury/MerCruiser | 98-8M0121940 | 47-8M0137221 |
| Mercury/MerCruiser | 47-8M0137221 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury models, it is critical to verify your engine's serial number against the requirements listed in the 'Notes' column to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | MerCruiser 4.5L | 4-Stroke | 47-8M0137221 | Requires serial number 2A531163 and above | ||
| Mercury | MerCruiser 6.2L MCM (sterndrive) | 4-Stroke | 47-8M0137221 | Requires serial number 2A531197 and above | ||
| Mercury | MerCruiser 6.2L MIE (inboard) | 4-Stroke | 47-8M0137221 | Requires serial number 2A530774 and above | ||
| Mercury | MerCruiser 6.2L TowSport | 4-Stroke | 47-8M0137221 | Requires serial number 2A531348 and above | ||
| Mercury | MerCruiser 4.3L MPI | 4-Stroke | 47-8M0137221 | Based on MarineEngineParts listing | ||
| Mercury | MerCruiser 5.0L MPI | 4-Stroke | 47-8M0137221 | Based on MarineEngineParts listing | ||
| Mercury | MerCruiser 350 MAG MPI | 4-Stroke | 47-8M0137221 | Based on MarineEngineParts listing |
Technical Specs
- Product Type
- Heavy Duty Sea Water Pump Impeller Kit
- Installation
- Direct replacement
- Dimensions
- Impeller Diameter: 2-5/8" (66.7 mm), Impeller Length: 2" (50.8 mm)
- Weight
- 1.00 lb (0.45 kg)
- Other Technical Attributes
- 8 blade impeller, 0.030" shorter than standard
What’s in the Box
- 1 x Shorter Heavy Duty Impeller (8M0103389)
- 1 x Rear Wear Plate
- 1 x Overmolded Inner (Front) Wear Plate (8M0072979)
- 1 x Outer Wear Plate with Seal (8M0114788)
Installation Notes
- Before starting, disconnect the boat's battery and close the engine's water inlet seacock.
- Locate the sea water pump on the engine block. Place a rag or bucket underneath to catch any spilled coolant.
- Loosen the hose clamps and carefully detach the inlet and outlet hoses from the pump housing.
- Remove the bolts securing the pump's front cover or housing plate.
- Pry the old impeller out of the housing with pliers. Note the rotational direction of the vanes for reinstallation.
- Remove the old wear plates and seals from the housing and cover. Clean all surfaces thoroughly.
- Install the new rear and front wear plates from the kit. Ensure they sit flat and are properly aligned.
- Lubricate the inside of the pump housing and the new impeller with a water-based marine lubricant or glycerine.
- Install the new impeller by pushing it into the housing while twisting it in the direction of engine rotation to bend the vanes correctly.
- Reinstall the front cover with its new seal/o-ring, ensuring the bolts are tightened evenly to spec.
- Reconnect the water hoses and tighten the clamps securely. Open the seacock.
- Reconnect the battery. Start the engine and immediately check the pump and hose connections for leaks. Verify water is exiting the exhaust/tell-tale.
Troubleshooting & FAQ
How do I confirm this impeller kit fits my MerCruiser engine?
Fitment for the 4.5L and 6.2L engines is determined by serial number. Please check the 'Engine & Model Compatibility' table and compare the required serial number range with your engine's number. Do not rely on model year alone.
Why is this impeller 0.030" shorter than the standard one?
This specific impeller is intentionally designed to be slightly shorter for certain MerCruiser sea water pump housings. This design change, paired with the included overmolded wear plates, helps resolve issues of impeller swelling and seizing in some late-model pumps, improving durability and reliability.
What are the signs of a failing sea water pump impeller?
Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent stream of water from the tell-tale outlet, visible cracks or missing vanes on the old impeller upon inspection, and a noticeable decrease in engine cooling performance.
How often should I replace my engine's impeller?
As a general preventative maintenance rule, it is recommended to inspect your sea water pump impeller annually and replace it every 1-2 years or every 100-200 hours of operation, whichever comes first. This interval can be shorter in saltwater or high-debris environments.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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