Water Pump Impeller Maintenance Kit – Fits Mercury/Mariner/Tohatsu 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0)

$45.99 $73.00

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Water Pump Impeller Maintenance Kit – Fits Mercury/Mariner/Tohatsu 4-6 HP 4-Stroke (Replaces 8M0120836, 3GR-87500-0) is backordered and will ship as soon as it is back in stock.

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

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Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This Water Pump Impeller Maintenance Kit provides essential components for servicing the cooling system on Mercury/Mariner 4-6 HP 4-Stroke outboard engines (serial numbers 0R411838 and above) and compatible Tohatsu 4-6 HP 4-Stroke models.

It serves as a direct aftermarket replacement for Mercury part number 8M0120836 and Tohatsu part number 3GR-87500-0.

Designed for direct replacement and straightforward installation.
Includes all essential parts for a comprehensive cooling system service.
Restores cooling efficiency and promotes engine longevity.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
Mercury	8M0120836
Tohatsu	3GR-87500-0

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury & Mariner models, this kit fits 4/5/6 HP EFI 4-Stroke outboards (2015 and newer) with serial number 0R411838 and higher. It is also compatible with Tohatsu MFS4, MFS5, and MFS6 4-Stroke models; please verify fitment against your service manual as specific year ranges are unconfirmed.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	4 HP EFI	4	4-Stroke	2015 and up	8M0120836	Serial number 0R411838 and above
Mercury	5 HP EFI	5	4-Stroke	2015 and up	8M0120836	Serial number 0R411838 and above
Mercury	6 HP EFI	6	4-Stroke	2015 and up	8M0120836	Serial number 0R411838 and above

Technical Specs

Product Type: Outboard Maintenance Service Kit
Installation: Direct replacement
Fuel Type: Gasoline
Weight: 0.21 kg (0.46 lb)
Package Dimensions: Approximately 100 × 92 × 76 mm (3.88 × 3.63 × 3.00 in)
Purpose: For cooling system maintenance and general service

What’s in the Box

1 x Water Pump Impeller (47-16154-3)
1 x Cotter Pin (8150264)
1 x Pin Key (28-16155)
1 x Thermostat (804540)
1 x Thermostat Gasket (27-8M0214960)
1 x O-Ring (25-16131)
1 x Oil Seal (26-16130)
1 x Fuel Filter (35-8M0157133)
1 x Gaskets (8035161)
2 x Drain Gasket (27-95220)

Installation Notes

Disconnect the engine's battery and remove the spark plug wire to prevent accidental starting.
Access the lower unit by disconnecting any shift linkage and removing the bolts securing it to the midsection.
Carefully remove the lower unit from the outboard's main housing.
Locate and open the water pump housing on top of the gearcase by removing the retaining bolts.
Remove the old impeller and associated components, noting their orientation for reassembly.
Clean the pump housing thoroughly before installing the new components.
Install the new impeller with a slight twisting motion in the correct rotational direction.
Reassemble the pump housing with the new gaskets and seals from the kit.
Reattach the lower unit, ensuring the driveshaft and water tube are properly aligned.
Reconnect the battery and test the engine with a water supply to confirm proper cooling system function.

Troubleshooting & FAQ

Which engines does this kit fit?

It is designed for Mercury/Mariner 4-6 HP 4-Stroke EFI outboards (2015+) with serial numbers 0R411838 and up. It is also made to fit compatible Tohatsu MFS4, MFS5, and MFS6 4-Stroke models.

How do I confirm this is the right part?

For Mercury/Mariner, match your engine's serial number to the specified range (0R411838 and above). For all engines, we strongly recommend visually comparing your old parts to the photos in this listing before ordering.

What are the signs of a bad water pump impeller?

Common symptoms include a weak or non-existent water stream from the telltale outlet, engine overheating alarms, steam from the exhaust, and reduced overall engine performance.

How often should I service the water pump?

For preventative maintenance, it is best practice to replace the impeller and gaskets every 100-200 hours of use or at least once per year, whichever comes first. Service intervals should be shorter if operating in saltwater or debris-heavy water.

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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