GASKET – Fits Mercury/Mercruiser Outboards 20, 200 (Replaces Mercury 27-39625, Aqua Power 309, Sierra 18-2828)

$4.20 $6.00

Shipping calculated at checkout.

GASKET – Fits Mercury/Mercruiser Outboards 20, 200 (Replaces Mercury 27-39625, Aqua Power 309, Sierra 18-2828) is backordered and will ship as soon as it is back in stock.

Worry-free returns

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).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

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 high-quality water pump GASKET – Fits Mercury/Mercruiser Outboards 20, 200 provides a reliable seal for the water pump assembly. It is designed for various Mercury 20 HP and 200 HP outboard models across multiple years, ensuring proper cooling system function.

This part is a direct interchange for Mercury 27-39625, Aqua Power 309, and Sierra 18-2828.

Installs between the water pump plate and base.

Part Number Matrix

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

Brand	Part Number
Mercury	27-39625
Aqua Power	309
Sierra	18-2828

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury/Mercruiser engines, check your serial number range or model year to ensure a correct fit.

Brand	Model	Rated HP	Years	OEM Part No.	Notes
Mercury	200	200	1985 & Below	27-39625	Used in Electrical, Exhaust/Cooling Systems, Instruments/Gauges, Trim/Tilt/Lift Systems
Mercury	20	20		27-39625	Water Pump Gasket
Mercury	200	200	1866496–2296266	27-39625
Mercury	200	200	2296267–2827676	27-39625
Mercury	200	200	2827677–3226957	27-39625
Mercury	200	200	3226958–3537530	27-39625
Mercury	200	200	3537531–4709592	27-39625
Mercury	200	200	7012358–7098522	27-39625
Mercury	200	200	8006265–8045198	27-39625
Mercury	200	200	9016254–9157229	27-39625
Mercury	200	200	4709593 & Up	27-39625
Mercury	200	200	7098523 & Up	27-39625
Mercury	200	200	8045199 & Up	27-39625
Mercury	200	200	9157230 & Up	27-39625
Mercury	Mercury Quicksilver Water Pump	200		27-39625
Mercury	Mercury Quicksilver Water Pump	20		27-39625

Technical Specs

Product Type: Gasket
Installation: Plate to Base (Water Pump)
Dimensions: Length: 1.06 in; Width: 7.5 in; Height: 6.0 in
Weight: 0.00 lbs (0.00 kg)

What’s in the Box

1 x GASKET (27-39625)

Installation Notes

Disconnect the negative battery terminal to prevent accidental starting.
If applicable, drain the engine's cooling system to minimize coolant loss.
Remove the lower unit (gearcase) from the outboard motor. Refer to your service manual for the correct procedure.
Locate and unbolt the water pump housing to access the old gasket.
Carefully remove the used gasket. Thoroughly clean both mating surfaces to remove any old gasket material or sealant residue.
Position the new gasket correctly on the cleaned surface.
Reinstall the water pump housing, ensuring bolts are tightened evenly to the manufacturer's specified torque.
Re-attach the lower unit to the outboard motor.
Reconnect the battery, refill the cooling system if drained, and run the engine to check for leaks and proper water circulation.

Troubleshooting & FAQ

How do I know if this gasket is failing?

Signs of a faulty water pump gasket include visible water leaks around the lower unit's seam, engine overheating alarms, or a weak or inconsistent stream from the tell-tale (water indicator) outlet.

Is this the correct gasket for my specific engine?

This gasket fits a range of Mercury 20 HP and 200 HP outboards. To ensure a perfect match, please consult the compatibility table and verify your engine's model, year, or serial number against the listed ranges.

Do I need to apply any sealant with this gasket?

Typically, this gasket is installed dry on clean, flat surfaces. However, it is always best to consult your engine’s official service manual, as some specific applications might recommend a thin layer of a non-hardening sealant.

What causes a water pump gasket to fail?

Failures are often due to age, heat cycles causing the material to become brittle, improper installation (uneven torque), or damage from debris in the cooling system. Regular impeller service is a good time to inspect and replace gaskets.

Why do some stores sell these in packs of 5?

Some suppliers bundle gaskets for professional marine technicians who use them frequently. Our listing is for a single gasket, allowing you to purchase only the quantity you need.

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.

Payment & Security

Payment methods

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.