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Manifold Gasket – Fits Ford 2.3L/140 CID Engines (Replaces OMC 913393, Sierra 18-0401)

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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.).

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 Manifold Gasket – Fits Ford 2.3L/140 CID Engines is engineered for Ford 2.3L/140 CID marine engines, commonly found in OMC Cobra stern drives from the late 1980s through the early 1990s. It provides a reliable seal between the exhaust manifold and the engine block.

It serves as a direct replacement for OMC part number 913393 and Sierra part number 18-0401.

  • Installs between the exhaust manifold and engine block.
  • Designed for gasoline-powered marine engines.
  • Built to withstand the harsh marine environment.

Part Number Matrix

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

Brand Part Number
OMC 913393
Sierra 18-0401

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This gasket is specifically for OMC Cobra applications using the Ford 2.3L engine.

Brand Model Rated HP Stroke Years OEM Part No.
OMC Cobra with Ford 2.3L 140 4-Stroke Late 1980s–1990s 913393

Technical Specs

Product Type
Exhaust Manifold Gasket
Installation Location
Between exhaust manifold and engine block
Fuel Type
Gasoline
Dimensions
22.0 cm x 7.0 cm x 1.13 cm (8.66" x 2.76" x 0.44")
Weight
0.02 kg (0.04 lbs)
Other Attributes
Designed for marine applications with Ford 2.3L/140 CID engines

What’s in the Box

  • 1 x Manifold Gasket

Installation Notes

  1. Ensure the engine is completely cool and disconnect the battery.
  2. Drain the engine coolant to a level below the exhaust manifold.
  3. Disconnect any hoses, sensors, or wires attached to the exhaust manifold.
  4. Carefully unbolt and remove the exhaust manifold from the engine block.
  5. Thoroughly clean both the manifold and engine block mating surfaces, removing all old gasket material and debris.
  6. Position the new gasket correctly on the engine block.
  7. Reinstall the exhaust manifold and tighten the bolts to the manufacturer's specified torque sequence and values.
  8. Reconnect all hoses, sensors, and wires, and refill the engine coolant.
  9. Start the engine and check carefully for any exhaust or coolant leaks.

Troubleshooting & FAQ

How do I know if this gasket will fit my engine?

This gasket is specifically designed for Ford 2.3L (140 CID) engines used in OMC Cobra stern drives during the late 1980s and early 1990s. Always cross-reference your existing part number with the ones listed (OMC 913393, Sierra 18-0401) and check the compatibility table.

What are the signs of a failed manifold gasket?

Common symptoms include a noticeable exhaust leak (loud ticking or hissing from the engine bay), decreased engine performance, visible soot or black streaks around the manifold, and potential water leaks into the cylinders if the manifold is water-cooled.

Do I need to use sealant with this gasket?

Generally, modern manifold gaskets like this are designed to be installed dry without any additional sealant. Always consult your engine's service manual for the official recommendation, as some applications may have specific requirements.

What is the difference between this and an OEM gasket?

This is an aftermarket replacement part, not OEM. It is engineered to meet or exceed original equipment manufacturer (OEM) specifications for fit, form, and function, providing a reliable and cost-effective alternative.

How often should a manifold gasket be replaced?

Exhaust manifold gaskets do not have a fixed replacement interval. They should be replaced whenever the exhaust manifold is removed or if signs of a leak are detected.

Can I reuse my old manifold bolts?

It is best practice to use new bolts when replacing an exhaust manifold or gasket, as old bolts can stretch, weaken, or corrode, leading to improper torque and potential leaks. Check your service manual for bolt specifications.

Is this part OEM or 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.

What are the shipping speed and cost?

We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

What is the warranty and return policy?

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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