Sea Water Pump Rebuild Kit – Fits Yanmar 2GM, 3GM, 2YM, 3YM Series (Replaces Yanmar 128377-42500, 128397-42500)

$47.60 $76.00

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Sea Water Pump Rebuild Kit – Fits Yanmar 2GM, 3GM, 2YM, 3YM Series (Replaces Yanmar 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 Major Rebuild Kit – Fits Yanmar 2GM, 3GM Series provides all necessary components for overhauling the sea water pump on European-built Yanmar GM-YEU series diesel engines manufactured between 1996 and 2004. It is designed for pumps with a 6-bolt cover measuring 76mm (3") in diameter.

The kit serves as a direct replacement for multiple Yanmar and Johnson part numbers, including 128377-42500, 128397-42500, and 10-24509-01, ensuring a precise fit and restoring original performance.

Engineered for direct OEM-level fitment and performance.
Specifically for European-built models with an E-prefix serial number.
Includes a new impeller, bearings, seals, end cover, and stainless steel screws.

Part Number Matrix

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

Brand	Part Number	Notes
Yanmar	128377-42500
Yanmar	128397-42500
Yanmar	128990-42500
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/year in the table below.

This kit is specifically designed for European-built Yanmar engines indicated by an "E-" prefix in the serial number.

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
Yanmar	3GM30F-YEU	30	4-Stroke	1996–2004	128377-42500	E-prefix serial number

Technical Specs

Product Type: Sea Water Pump Major Rebuild Kit
Installation: Direct OEM Replacement
Fuel Type: Diesel
Connection: Direct Mount
Housing Color: Black
Dimensions: Kit fits 6-bolt cover with 76mm (3") diameter
Other Technical Attributes: Impeller: 2" (50.8mm) diameter, 0.87" (22mm) width, 0.47" (12mm) shaft, 6 blades

What’s in the Box

1 x Water Pump Impeller (128991-42200/128990-42200)
1 x Pump End Cover O-ring (X02173476)
1 x Slinger O-ring (X02173432)
1 x Retaining Ring (X00370012)
1 x Retaining Ring (X00371732)
1 x Spacer Plate (X0145050)
1 x Bearing (X03431760)
1 x Bearing (X03431748)
1 x SS Screws Set (X0504163)
1 x Lip Seal (X02233010)
1 x End Cover (X0142398/128990-42540)

Installation Notes

Turn off the engine and close the sea cock (sea water intake valve).
Drain the existing sea water from the pump by loosening the drain plug.
Loosen the hose clamps and remove the inlet and outlet hoses from the pump.
Remove the bolts securing the pump to the engine and carefully detach the pump.
Disassemble the old pump, noting the order and orientation of each component. Pay close attention to the seals and bearings.
Clean all reusable parts and the pump mounting surface on the engine.
Install the new bearings, seals, and other components from the kit into the pump housing, using appropriate lubricant for seals.
Reassemble the pump, ensuring the new end cover and O-ring are correctly seated. Tighten the cover screws in a star pattern.
Mount the new pump assembly onto the engine and tighten the mounting bolts to the manufacturer's recommended torque.
Reconnect the water hoses and tighten the clamps securely.
Open the sea cock, start the engine, and immediately check for any leaks around the pump and hoses.
Allow the engine to run and verify normal water flow from the exhaust.

Troubleshooting & FAQ

How do I know if this kit fits my engine?

This kit is specifically for Yanmar's European-built 2GM-YEU and 3GM-YEU series engines made from 1996–2004. The key identifier is an "E" prefix in your engine's serial number. It fits pumps with a 6-bolt cover that is 76mm (3") in diameter. Do not use this kit for Japanese or other non-YEU models.

What are the signs my sea water pump needs a rebuild?

Common signs of pump failure include water leaks from the pump body, reduced water flow from the exhaust outlet, and engine overheating at idle or low speeds. A worn impeller or failing bearings can cause these symptoms.

How often should the sea water pump be serviced?

The impeller should be inspected annually and replaced every 1-2 years, depending on usage and water conditions. A full rebuild with a major kit like this is recommended every 3-5 years or if you notice leaks or performance degradation.

What's the difference between this and a minor rebuild kit?

A minor kit typically only includes the impeller, gasket/O-ring, and sometimes cover screws. This major rebuild kit includes all those parts plus critical internal components like bearings, lip seals, retaining rings, and a new end cover, allowing for a full overhaul of the pump.

Is there anything I should check before installation?

Absolutely. Before starting, compare the new end cover and impeller dimensions with your old parts. Ensure your pump has a 6-bolt cover. Verifying these key features against your existing hardware is the best way to guarantee a correct fit.

Can I install this kit myself?

If you have experience with marine engine maintenance, this is a manageable task. However, due to the importance of the cooling system, we recommend professional installation if you are not completely confident. Incorrect assembly can lead to leaks and engine damage.

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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