Cylinder Head Gasket – Fits Mercury 40-50 HP 4-Stroke (Replaces 27-825032, 825032)

$85.00 $136.00

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Cylinder Head Gasket – Fits Mercury 40-50 HP 4-Stroke (Replaces 27-825032, 825032) is backordered and will ship as soon as it is back in stock.

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Product Details

This aftermarket Cylinder Head Gasket is engineered to fit Mercury 40-50 HP 4-Stroke outboard engines manufactured from 1996–2005 (serial numbers 0G231123 through 0T1748499). It provides a reliable seal for the cylinder head, ensuring optimal engine compression and performance.

It serves as a direct cross-reference for Sierra 18-3845, WSM 18-3845, and Mercury OEM part numbers 27-825032 and 825032.

Designed for a straightforward OEM-level replacement installation.
Suitable for 4-cylinder, 4-stroke gasoline outboard engines.
This package includes one cylinder head gasket.

Part Number Matrix

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

Brand	Part Number
Mercury	27-825032
Mercury	825032
Sierra	18-3845
WSM	18-3845

Engine & Model Compatibility

Confirm your engine model and year in the table below. It is critical to also verify your engine's serial number falls within the specified range (0G231123 - 0T1748499).

For Mercury & Mariner Engines: This gasket fits specific 40, 45, and 50 HP 4-stroke models, including Bigfoot and regional variants like Bodensee and Italy models, within the 1996–2005 year range.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	40	40	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499
Mercury	45	45	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499, Bodensee model
Mercury	50	50	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499
Mercury	50 Bigfoot	50	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499
Mariner	40	40	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499, Italy model
Mariner	45 Bodensee	45	4-Stroke	1996–2005	27-825032	s/n 0G231123 - 0T1748499

Technical Specs

Product Type: Cylinder Head Gasket
Installation: OEM Replacement
Fuel Type: Gasoline
Other Technical Attributes: For 4-cylinder engines
Weight: 0.082 kg (0.18 lb)
Dimensions: 46.0 cm L x 19.0 cm W x 0.5 cm H

What’s in the Box

1 x Cylinder Head Gasket (Replaces 27-825032)

Installation Notes

Disconnect the battery and relieve any pressure from the fuel system.
Drain the engine coolant completely from the block.
Remove the valve cover, intake manifold, exhaust manifold, and any other components obstructing access to the cylinder head.
Following the manufacturer's service manual, loosen and remove the cylinder head bolts in the specified sequence (typically reverse of the tightening order).
Carefully lift the cylinder head straight up off the engine block. Avoid prying or damaging the mating surfaces.
Thoroughly clean all old gasket material, sealant, oil, and debris from both the cylinder head and engine block mating surfaces.
Inspect both surfaces for warping or damage using a precision straightedge and feeler gauge.
Position the new head gasket correctly on the engine block, ensuring proper alignment with dowel pins and bolt holes. Do not use sealant unless explicitly required by the service manual.
Carefully reinstall the cylinder head.
Install new or inspected head bolts and tighten them in the correct sequence and torque stages as specified by the manufacturer. This is critical for a proper seal.
Reassemble all components removed in the earlier steps.
Refill the cooling system, reconnect the battery, and start the engine, checking carefully for any fluid leaks or performance issues.

Troubleshooting & FAQ

How do I confirm this gasket fits my specific engine model?

Check your engine's serial number. This part is designed for Mercury and Mariner models with serial numbers ranging from 0G231123 to 0T1748499. Consult the Engine & Model Compatibility table on this page for a detailed list of approved models, horsepowers, and years.

What are the most common signs of a failed cylinder head gasket?

Common symptoms include engine overheating, a noticeable loss of power, persistent white smoke from the exhaust (which indicates coolant is burning), milky or frothy engine oil (a sign of coolant mixing with oil), or external coolant and oil leaks from the seam between the cylinder head and the engine block.

Can I reuse a cylinder head gasket after removing the head?

No. Cylinder head gaskets are designed as single-use "crush" components. They permanently deform upon installation and torquing to create a perfect seal. Once removed, they cannot provide a reliable seal and must be replaced with a new one.

Is any special sealant required for installation?

Generally, no. This gasket is designed to be installed dry onto clean, flat surfaces. Applying sealant can interfere with its sealing properties and may lead to improper torque readings or even engine damage. Always follow the specific instructions in your engine's official service manual.

What's the difference between this and the original Mercury part?

This is a high-quality aftermarket part engineered to meet or exceed original equipment manufacturer (OEM) specifications for fit, form, and function. Since the original Mercury part (27-825032) is largely discontinued or unavailable, our replacement provides a reliable and cost-effective alternative without compromising on quality.

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

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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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