Valve Cover Gasket – Fits Mercruiser 3.7L 224 CID 4-Cylinder (Replaces 27-73666)

$27.50

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Product Details

This replacement Valve Cover Gasket – Fits Mercruiser 3.7L 224 CID 4-Cylinder (Replaces 27-73666) is engineered for a precise fit on Mercruiser 3.7L (224 CID) 4-Cylinder engines, including models from 165 to 190 HP, manufactured between 1976 and 1989. It creates a reliable seal to prevent oil leaks from the engine's valve cover.

This part offers a direct interchange for Mercury/Mercruiser 27-73666, Sierra 18-0685, GLM 31820, and VICVS50176TC, ensuring compatibility with multiple systems.

Installs as a direct replacement for the original part.
Made from a durable cork/rubber composite for a dependable seal.
Sold as a single gasket for one valve cover.

Part Number Matrix

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

Brand	Part Number
Mercury/Mercruiser	27-73666
Sierra	18-0685
GLM	31820
VIC	VS50176TC

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This part is designed specifically for the Mercruiser engine models listed. Please check your engine's serial number range for an exact match.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercruiser	165 (2 BBL.)	165	4-Stroke	1987	27-73666	Serial Range: 0B434941–0B774251
Mercruiser	165 (2 BBL.)	165	4-Stroke	1988–1989	27-73666	Serial Range: 0B774252 & Up
Mercruiser	170 (2 BBL.)	170	4-Stroke	1985–1986	27-73666	Serial Range: 6916779–0B434940
Mercruiser	170 (2 BBL.)	170	4-Stroke	1987–1989	27-73666
Mercruiser	180 (4 BBL.)	180	4-Stroke	1985–1986	27-73666
Mercruiser	180 (4 BBL.)	180	4-Stroke	1987	27-73666	Serial Range: 0B436391–0B775248
Mercruiser	180 (4 BBL.)	180	4-Stroke	1988-1989	27-73666
Mercruiser	190 (4 BBL.)	190	4-Stroke	1985–1986	27-73666	Serial Range: 6916779–0B436390
Mercruiser	190 (4 BBL.)	190	4-Stroke	1987–1989	27-73666
Mercruiser	3.7L (2 BBL.)	165–190	4-Stroke	1985–1987	27-73666
Mercruiser	3.7L (2 BBL.)	165	4-Stroke	1988–1989	27-73666	Serial Range: 0B774252 & Up
Mercruiser	3.7LX (4 BBL.)	165–190	4-Stroke	1985–1987	27-73666
Mercruiser	3.7LX (4 BBL.)	165	4-Stroke	1988–1989	27-73666	Serial Range: 0B775249 & Up
Mercruiser	470 (2 BBL.)		4-Stroke	1976-1979	27-73666	Serial Range: 4208730–5520114
Mercruiser	470 (2 BBL.)		4-Stroke	1980–1982	27-73666	Serial Range: 5520115–6218036
Mercruiser	470 (2 BBL.)		4-Stroke	1983-1984	27-73666	Serial Range: 6218037-6916778
Mercruiser	470 MIE		4-Stroke	1980–1983	27-73666
Mercruiser	485 (2 BBL.)		4-Stroke	1980–1982	27-73666	Serial Range: 5685394–6218036
Mercruiser	488 (4 BBL.)		4-Stroke	1983-1984	27-73666	Serial Range: 6170297–6916778

Technical Specs

Product Type: Valve Cover Gasket
Installation: Direct Replacement
Fuel Type: Gasoline
Housing Material: Cork/Rubber Composite
Housing Color: Brown/Natural
Dimensions: 69.00 × 18.00 × 1.00 inches
Weight: 0.09 lbs (0.04 kg)
Fitting Type: Valve Cover
Other Attributes: Sold as a single gasket

What’s in the Box

1 x Valve Cover Gasket (27-73666)

Installation Notes

Disconnect the battery before beginning work. Ensure the engine is cool.
Remove any components obstructing access to the valve cover.
Unbolt and carefully remove the valve cover. If it is stuck, gently tap the side with a rubber mallet; do not pry between mating surfaces.
Remove the old gasket and thoroughly clean any residual gasket material, oil, or debris from both the cylinder head and the valve cover sealing surfaces.
Position the new gasket onto the valve cover, ensuring it is properly seated in the groove or aligned with the bolt holes.
Reinstall the valve cover and hand-tighten the bolts.
Using a torque wrench, tighten the bolts in the sequence and to the value specified in your engine's service manual to ensure even pressure.
Reconnect any components that were removed and reconnect the battery. Start the engine and check for leaks.

Troubleshooting & FAQ

How do I know if my valve cover gasket is failing?

Common signs include visible oil leaks running down the side of the engine block from the valve cover, a burning oil smell as oil drips onto hot exhaust components, and unexplained low engine oil levels.

Is this gasket reusable?

No, valve cover gaskets are designed for a single use. Reusing an old gasket will likely result in leaks, as it has already been compressed and heat-cycled.

Do I need to use sealant with this gasket?

This cork/rubber composite gasket is designed to be installed dry. However, it is standard practice to apply a small amount of RTV sealant at any sharp corners or seams, such as where the timing cover or intake manifold meet the cylinder head. Always consult your service manual for specific recommendations.

What is the torque sequence for the valve cover bolts?

The correct torque value and tightening sequence are critical for a leak-free seal and to avoid damaging the valve cover. This information is specific to your engine and can be found in the official service manual for your Mercruiser model.

Is there a recommended replacement interval?

There is no fixed replacement interval. Gaskets should be replaced whenever the valve cover is removed for service (e.g., valve adjustment) or as soon as any signs of leaking are detected.

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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