Water Pump Repair Kit – Fits Mercury/Mariner 25-50 HP (Replaces 821354A2, 821354A1, 821354A04)

$28.99 $46.00

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Water Pump Repair Kit – Fits Mercury/Mariner 25-50 HP (Replaces 821354A2, 821354A1, 821354A04) 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.).

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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 Water Pump Repair Kit – Fits Mercury/Mariner 25-50 HP provides all necessary components to restore your engine's cooling system. It is designed for a broad range of Mercury/Mariner 2-stroke and 4-stroke models from 1998–2018, as well as Force 40-50 HP outboards from 1995–1997. Regular impeller and seal replacement prevents overheating and ensures long-term engine reliability.

Engineered as a direct replacement, this kit serves as an aftermarket equivalent for Mercury parts 821354A2, 821354A1, and 821354A04. It also interchanges with Sierra 18-4531, GLM 12045, and SEI 3219.

Installs directly into the lower unit housing.
Built with corrosion-resistant marine-grade materials for saltwater and freshwater use.
Includes a neoprene impeller, wear plate, gaskets, and seals for a complete service.

Part Number Matrix

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

Brand	Part Number
Mercury	821354A2
Mercury	821354A1
Mercury	821354A04
Sierra	18-4531
GLM	12045
SEI	3219

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Fits various Mercury and Mariner outboards from 25 to 50 HP. Please check your serial number range against the notes column.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury/Mariner	Four Stroke	25	4-Stroke	1998–2018	821354A2	Carb 0G590000 - 0T408999
Mercury/Mariner	Four Stroke	30	4-Stroke	1998–2018	821354A2	Carb 0G760300 - 0T408999
Mercury/Mariner	Four Stroke	30	4-Stroke	1998–2018	821354A2	Jet 0G590000 and up
Mercury/Mariner	Two Cylinder	30/40	2-Stroke	1998–2018	821354A2	0G053314 and up
Mercury/Mariner	Four Stroke	40/45	4-Stroke	1998–2018	821354A2	2:1 0G760300 - 0T408999
Mercury/Mariner	Four Stroke	45	4-Stroke	1998–2018	821354A2	Bodensee 0G231123 and up
Mercury/Mariner	Three Cylinder	40	2-Stroke	1998–2018	821354A2	0G531301 and up
Mercury/Mariner	Three Cylinder	50	2-Stroke	1998–2018	821354A2	0G590000 and up
Mercury/Mariner	Four Stroke	50	4-Stroke	1998–2018	821354A2	0G231123 and up
Mercury/Mariner	BigFoot	50	4-Stroke	1998–2018	821354A2	0G760300 - 0T178499

Also compatible with select 2-stroke Force outboards. Verify your model's serial number falls within the specified range.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Force	Outboard	40	2-Stroke	1995–1997	821354A2	0E288000 - 0E369299
Force	Outboard	50	2-Stroke	1995–1997	821354A2	0E288000 - 0E369299

Technical Specs

Product Type: Water Pump Repair Kit
Installation: Direct replacement for lower unit
Housing Material: Metal alloy (base plate), neoprene rubber (impeller)
Housing Color: Black (impeller), metallic (plate)
Weight: 0.2 kg (0.45 lb)
Fitting Type: Direct fit
Other Technical Attributes: Corrosion-resistant marine-grade materials
Warranty: Varies by seller (typically 1 year)

What’s in the Box

1 x Neoprene Impeller (47-85089-10, 47-85089-3)
1 x Wear Plate (8213542)
1 x Upper Gasket (27-822189)
1 x Lower Gasket (27-822217)
1 x Short Water Tube Seal (43023)
1 x Long Water Tube Seal (823547-1, 8235471)
2 x Washer (12-86645-1)
1 x Drive Key (85119)

Installation Notes

Disconnect the battery and remove the engine cover.
Drain the gearcase oil from the lower unit.
Remove the bolts securing the lower unit to the engine's upper section and carefully lower it.
Locate and unbolt the water pump housing.
Remove the old impeller, gaskets, wear plate, and seals. Clean all mating surfaces thoroughly.
Install the new wear plate, gaskets, and drive key.
Slide the new impeller onto the driveshaft, rotating it in the direction of engine operation.
Re-install the water pump housing, ensuring seals are correctly seated.
Re-attach the lower unit to the engine, making sure the driveshaft and water tube align.
Refill the gearcase with fresh oil and re-connect the battery.
Start the engine using a water supply (flushing muffs) and verify a steady stream of water from the tell-tale outlet.

Troubleshooting & FAQ

How can I confirm this kit fits my specific engine model?

The best way is to match your engine's model, horsepower, and year to the compatibility tables above. Most importantly, check that your engine's serial number falls within the specified range, as this is the most accurate fitment data.

What are the signs of a failing water pump impeller?

Common symptoms include a weak or intermittent water stream from the "tell-tale" outlet, engine overheating alarms, or a noticeable decrease in engine performance. A crack or tear in the tell-tale stream is a strong indicator.

How often should the water pump impeller be replaced?

For preventative maintenance, it is recommended to inspect and likely replace the impeller every 100-200 operating hours or at least once every two years, whichever comes first. This interval may be shorter if you frequently operate in sandy or silty water.

Is any special grease needed for installation?

Yes, it's highly recommended to apply a light coat of marine-grade grease or a soap-and-water solution to the inside of the pump housing and the impeller fins. This provides lubrication during the initial dry start-up before water circulates.

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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