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

$35.68 $57.00

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Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP Outboards (Replaces 821354A2) is backordered and will ship as soon as it is back in stock.

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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 25-50HP Outboards (Replaces 821354A2) is designed for Mercury and Mariner outboards from 25 to 50 HP, including both 2-stroke and 4-stroke models manufactured from 1994 through 2018. It also fits select Force outboard models from 1995–1999.

It serves as a direct replacement for several part numbers, including Mercury/Mariner 821354A2 (which supersedes 821354A1 and 821354A04) and aftermarket equivalents from Sierra, GLM, Pro Marine, and SEI Marine.

Engineered for direct OEM-level fit and function.
Constructed with a durable neoprene impeller and a stainless steel wear plate for longevity.
Includes all necessary gaskets, seals, and hardware for a complete overhaul.

Part Number Matrix

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

Brand	Part Number	Notes
Mercury/Mariner	821354A2	Supersedes 821354A1, 821354A04
Sierra	18-4531
GLM	12045
Pro Marine	3219 / 3219-1
SEI Marine	96-265-03BK

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This kit is designed for the following Mercury and Mariner outboard applications.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury/Mariner	25	25	4-Stroke	1998–2018	821354A2	Carb 0G590000–0T408999
Mercury/Mariner	30	30	2-Stroke	1994–2018	821354A2	2 Cylinder models
Mercury/Mariner	30	30	4-Stroke	1998–2018	821354A2
Mercury/Mariner	30 Jet	30	4-Stroke	1998–2018	821354A2	3 Cylinder models
Mercury/Mariner	40	40	2-Stroke	1994–2018	821354A2	2 & 3 Cylinder models
Mercury/Mariner	40	40	4-Stroke	1998–2018	821354A2
Mercury/Mariner	45 Bodensee	45	4-Stroke	1998–2018	821354A2	Special emission models
Mercury/Mariner	50	50	2-Stroke	1998–2018	821354A2	3 Cylinder models
Mercury/Mariner	50	50	4-Stroke	1998–2018	821354A2
Mercury/Mariner	50 Bigfoot	50	4-Stroke	1998–2018	821354A2

This kit is designed for the following Force outboard applications.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Force	40	40	2-Stroke	1995–1997	821354A2	Serial: 0E093700–0E287999
Force	50	50	2-Stroke	1995–1997	821354A2	Serial: 0E093700–0E287999

Technical Specs

Product Type: Water Pump Repair Kit
Installation: Direct OEM Replacement
Housing Material: Stainless Steel 316 (Plate)
Impeller Material: Neoprene Rubber
Tube Material: Nylon PA66
Dimensions: 152.4 × 114.3 × 38.1 mm (6 × 4.5 × 1.5 in) [packaging]
Weight: 0.18 kg (5.3 oz)
Warranty: 1 Year

What’s in the Box

1 × Water Pump Impeller (89640)
1 × Face Plate/Wear Plate (12505 821354-2)
2 × Water Tube Seal (85180 43023/85181 823547-1)
2 × Washer (31175 12-86645-1)
2 × Gasket (37490 27-822189/37700 27-822217)

Installation Notes

Disconnect the negative battery cable and remove the propeller for safety.
Place a drain pan under the gearcase, remove the drain and vent plugs, and drain the gear oil.
Remove the lower unit (gearcase) mounting bolts and carefully separate it from the engine.
Unbolt and remove the old water pump housing, impeller, and wear plate. Note the orientation of the impeller vanes.
Thoroughly clean the mounting surfaces, removing any old gasket material or sealant.
Install the new gaskets, wear plate, impeller, and housing. Lightly grease the interior of the housing and ensure the impeller vanes curve in the correct rotational direction.
Torque the water pump housing bolts to the manufacturer's specifications.
Reinstall the lower unit, ensuring the driveshaft, shift shaft, and water tube align correctly.
Refill the gearcase with new marine gear lubricant before reinstalling and tightening the drain/vent plugs.
Reconnect the battery, start the engine using a water supply (flushing muffs), and verify water is exiting the tell-tale port.

Troubleshooting & FAQ

How do I find my engine's serial number to confirm fitment?

The serial number is typically found on a plate or sticker on the transom bracket or the side of the engine block. The compatibility tables list specific serial number ranges for certain models, which is the most accurate way to verify this kit is correct for your outboard.

What are the signs of a failing water pump?

Common symptoms include a weak or non-existent water stream from the "tell-tale" outlet, engine overheating alarms, and in severe cases, steam from the exhaust. Reduced engine performance at high RPMs can also indicate poor cooling.

How often should I replace my water pump impeller?

For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years (or every 100-200 hours of use), depending on operating conditions. Operation in sandy or silty water may require more frequent service.

Why is my engine still overheating after installing the new kit?

First, confirm the installation was correct—especially the impeller vane direction and that all seals are seated properly. Other potential causes include blockages in the cooling water passages, a faulty thermostat, or debris clogging the water intake screens on the lower unit.

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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