Manifold Gasket – Fits Mercury Marine/Mercruiser (27-78409)
Manifold Gasket – Fits Mercury Marine/Mercruiser (27-78409) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Free standard shipping on all orders under 1 KG
Manifold Gasket – Fits Mercury Marine/Mercruiser (27-78409)
Product Details
This Manifold Gasket creates a secure seal between the baffle plate and manifold cover on specific Mercury Marine 20 HP 4-Stroke outboard engines. It is engineered to meet original equipment specifications for a reliable, leak-free fit.
It serves as a direct replacement for Mercury part numbers 27-78409, 2739316, and 2772915.
- Installs between the baffle plate and manifold cover.
- Engineered to meet OEM (Original Equipment Manufacturer) specifications.
- Includes one gasket per package.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 27-78409 |
| Mercury | 2739316 |
| Mercury | 2772915 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury | 200 | 20 | 4-Stroke | 27-78409 | For serial #4709593 & Up |
| Mercury | 200 | 20 | 4-Stroke | 27-78409 | For serial #7098523 & Up |
| Mercury | 200 | 20 | 4-Stroke | 27-78409 | For serial #8045199 & Up |
| Mercury | 200 | 20 | 4-Stroke | 27-78409 | For serial #9157230 & Up |
Technical Specs
- Product Type
- Gasket
- Installation
- Baffle Plate to Manifold Cover
- Dimensions
- 11.25 × 6.0 × 1.13 inches (286 × 152 × 29 mm)
- Weight
- 5 ounces (0.14 kg)
- Technical Attributes
- Built to OEM specifications
- Warranty
- Amazon.com Voluntary 30-Day Return Guarantee
What’s in the Box
- 1 x Gasket (27-78409)
Installation Notes
- Disconnect the vessel's battery and drain the engine cooling system before beginning work.
- Carefully remove the existing manifold cover and scrape away all remnants of the old gasket from both mating surfaces.
- Ensure both the manifold and cover surfaces are clean, dry, and free of debris or corrosion.
- Position the new gasket correctly over the alignment dowels or bolt holes. Do not use sealant unless explicitly required by your engine's service manual.
- Reinstall the manifold cover and tighten the bolts in the sequence and to the torque values specified by the manufacturer.
- Refill the cooling system, reconnect the battery, and start the engine, checking carefully for any exhaust or coolant leaks around the repaired area.
Troubleshooting & FAQ
How do I confirm this gasket fits my engine?
This gasket is for specific Mercury 20 HP 4-Stroke models. The most reliable way to confirm fitment is to match your engine's serial number to the ranges listed in the compatibility table and verify your original part number is 27-78409.
What are the signs of a failing manifold gasket?
Common signs include visible coolant or water leaks around the manifold, engine overheating, a significant loss of engine performance, white smoke from the exhaust, or finding water contamination in the engine oil (a "milky" appearance).
Should I use sealant with this gasket?
Typically, modern gaskets like this are designed to be installed dry. However, always consult the official service manual for your specific engine model. If the manual specifies a sealant, follow its recommendation.
When should this gasket be replaced?
There is no fixed service interval. This gasket should be replaced whenever the manifold cover is removed or if you detect any signs of failure, such as leaks or engine cooling problems.
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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