Gasket – Fits Mercury/Mariner 35HP & 40HP (Replaces 27-66847)

$4.99

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Product Details

This is a replacement Gasket for Mercury/Mariner 35HP & 40HP engines (Replaces 27-66847), designed to fit 2-cylinder 35HP and 40/402HP outboard models manufactured from 1986 and later. It ensures a proper seal for the coil mounting bracket to the engine block.

This part is a direct interchange for Mercury part number 27-66847 and Sierra part number 18-0650.

Installs between the coil mounting bracket and the engine block.
Designed for use in gasoline outboard engines.
Package includes one gasket.

Part Number Matrix

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

Brand	Part Number
Mercury	27-66847
Sierra	18-0650

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury and Mariner outboards, verify compatibility using your engine's serial number (S/N) which is crucial for models from 1986 and later.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	35 (2 CYL.)	35	2-Stroke	1986 and later	27-66847	Canada (S/N 209608 & Up)
Mercury	35 (2 CYL.)	35	2-Stroke	1986 and later	27-66847	USA (S/N 6445653 THRU 0B110788)
Mercury	35 (2 CYL.)	35	2-Stroke	1986 and later	27-66847	Belgium (S/N 9384476 & Up)
Mercury	35 (2 CYL.)	35	2-Stroke	1986 and later	27-66847	Belgium (S/N 9466647 & Up)
Mercury	35 (2 CYL.)	35	2-Stroke	1986 and later	27-66847	USA (S/N B110789 & Up)
Mercury	40/402 (2 CYL.)	40	2-Stroke	1986 and later	27-66847	USA (S/N 5556230 & Up)
Mercury	40/402 (2 CYL.)	40	2-Stroke	1986 and later	27-66847	Canada (S/N 7144763 & Up)
Mercury	40/402 (2 CYL.)	40	2-Stroke	1986 and later	27-66847	Australia (S/N 8064750 & Up)
Mercury	40/402 (2 CYL.)	40	2-Stroke	1986 and later	27-66847	Belgium (S/N 9251456 & Up)

Technical Specs

Product Type: Gasket
Installation: Coil Mounting Bracket to Engine Block
Fuel Type: Gasoline
Dimensions: 7.13" x 6.0" x 1.06"
Weight: 0.02 kg (0.04 lb)
Other Technical Attributes: Used on Mercury/Mariner 2-cylinder outboard engines

What’s in the Box

1 x Gasket, Coil Mounting Bracket to Block (27-66847)

Installation Notes

Disconnect the battery and ensure the engine is off and cool.
Locate and unbolt the coil mounting bracket from the engine block.
Carefully remove the old gasket and clean both mating surfaces of any residue or debris.
Position the new gasket correctly onto the engine block.
Re-mount the coil bracket over the new gasket.
Tighten the mounting bolts evenly and to the manufacturer's recommended torque specifications.
Reconnect the battery and test the engine for proper operation.

Troubleshooting & FAQ

How do I know if this gasket fits my specific engine serial number?

Check the compatibility table, which lists specific serial number (S/N) ranges for Mercury and Mariner models from 1986 and later. Always verify your engine's serial number against the provided ranges to ensure a perfect match.

What are the signs of a failing coil bracket gasket?

Symptoms of a faulty gasket can include rough idling, intermittent engine misfires, or physical signs of cracking and wear on the old gasket upon inspection. A loose coil can disrupt ignition timing and performance.

Is this gasket sold individually or in a pack?

This listing is for a single gasket. Please adjust the order quantity at checkout if you require multiple units for your project.

How often should this gasket be replaced?

We recommend replacing this gasket any time the coil mounting bracket is removed from the engine block for service. It does not have a set replacement interval, but it should be inspected for integrity during routine maintenance.

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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