Sea Water Pump – Fits Yanmar 2GM20/3GM30 Series (Replaces 128377-42500, 128397-42500)

$175.00 $280.00

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Sea Water Pump – Fits Yanmar 2GM20/3GM30 Series (Replaces 128377-42500, 128397-42500) 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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Delivery and Shipping

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 is a direct replacement Sea Water Pump designed specifically for Yanmar marine diesel engines in the GM-YEU series (European-built models from 1996–2004). It ensures reliable raw water circulation to maintain optimal engine temperature.

This part is a direct interchange for Yanmar part numbers 128377-42500, 128397-42500, 128990-42510, and Johnson Pump numbers 10-24509-01, 10-24509-02, 10-13337-01, 10-13492-01, and 10-13328-03.

Engineered for direct-mount installation.
Designed for use in marine diesel applications.
Includes a new impeller for a complete installation.

Part Number Matrix

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

Brand	Part Number	Notes
Yanmar	128377-42500
Yanmar	128397-42500
Yanmar	128990-42510
Johnson	10-24509-01
Johnson	10-24509-02
Johnson	10-13337-01
Johnson	10-13492-01
Johnson	10-13328-03	Reference

Engine & Model Compatibility

Confirm your engine model and year in the table below.

Note for Yanmar Owners: This pump fits GM-YEU series engines, which are European-built models typically designated by an "E" prefix on the engine serial number (e.g., E00123).

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Yanmar	2GM20-YEU	20	4-Stroke	1996–2004	128377-42500	E-prefix serial number
Yanmar	2GM20C-YEU	20	4-Stroke	1996–2004	128377-42500	E-prefix serial number
Yanmar	3GM30-YEU	30	4-Stroke	1996–2004	128377-42500	E-prefix serial number
Yanmar	3GM30C-YEU	30	4-Stroke	1996–2004	128377-42500	E-prefix serial number

Technical Specs

Product Type: Sea Water Pump (Raw Water Pump)
Installation: Direct OEM Replacement
Fuel Type: Diesel
Connection: Direct Mount
Housing Color: Black
Weight: 1.5 kg (3.3 lbs)
Included Impeller: 653-0001

What’s in the Box

1 x Sea Water Pump with Bracket
1 x Impeller (653-0001)

Installation Notes

Close the raw water seacock.
Place a container below the pump to catch any residual water.
Loosen the hose clamps and carefully remove the inlet and outlet hoses.
Remove the mounting bolts securing the pump to the engine bracket.
Carefully remove the old pump assembly.
Clean the mounting surface to ensure a proper seal.
Mount the new sea water pump, ensuring it is correctly aligned.
Tighten the mounting bolts to the manufacturer's recommended torque specifications.
Reconnect the water hoses and securely tighten the clamps.
Open the seacock.
Start the engine and immediately check for any leaks around the pump and hose connections.

Troubleshooting & FAQ

How do I confirm this pump fits my Yanmar engine?

This pump is specifically for Yanmar GM-YEU series engines (2GM20 and 3GM30 models) manufactured between 1996-2004. These European models are identified by an "E" at the start of the engine serial number. Please verify your model and serial prefix before ordering.

My engine is a 3YM30, will this fit?

While some sources suggest potential compatibility with the YM series (2YM15, 3YM20, 3YM30), it has not been verified by the manufacturer. We only guarantee fitment for the specified GM-YEU models listed in the compatibility table.

What are the signs of a failing sea water pump?

Common signs include engine overheating, a 'low raw water flow' alarm, visible water leaks from the pump housing or weep holes, a damaged impeller, or unusual grinding/squealing noises from the pump assembly.

How often should the impeller be replaced?

As a best practice for preventative maintenance, impellers should be inspected annually and replaced every 1-2 years or every 200-300 engine hours, whichever comes first. Always replace it if you notice cracks, missing vanes, or hardening of the rubber.

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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