Gasket – Fits Mercury Quicksilver Outboard Engines (Replaces 27-25725)

$2.95 $4.00

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Gasket – Fits Mercury Quicksilver Outboard Engines (Replaces 27-25725) is backordered and will ship as soon as it is back in stock.

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Product Details

This Gasket – Fits Mercury Quicksilver Outboard Engines (Replaces 27-25725) provides a reliable seal for the magneto end cap cover on various Mercury 4-cylinder outboard engines. It is engineered for models ranging from 30 to 65 HP manufactured between 1956 and 1975.

This part is a direct cross-reference for Quicksilver OEM part number 27-25725 and other equivalents.

Installs on the magneto end cap cover.
Designed to ensure a tight, reliable seal against the elements.

Part Number Matrix

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

Brand	Part Number
Quicksilver / Mercury	27-25725
OMC / Johnson / Evinrude	0508669

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This gasket is confirmed to fit the following Mercury outboard models. Please check your engine's serial number if a specific range is noted.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	300	30	2-Stroke	1960–1966	27-25725
Mercury	350	35	2-Stroke	1960–1966	27-25725
Mercury	Mark 35A	35	2-Stroke	1958–1959	27-25725
Mercury	400	40	2-Stroke	1960–1966	27-25725
Mercury	450	45	2-Stroke	1960–1966	27-25725
Mercury	Mark 55	40	2-Stroke	1956–1958	27-25725	With Kiekhaefer magneto
Mercury	Mark 55A	45	2-Stroke	1958–1959	27-25725
Mercury	500	50	2-Stroke	1960–1966	27-25725
Mercury	Mark 58	45	2-Stroke	1958–1959	27-25725
Mercury	Mark 58A	45	2-Stroke	1958–1959	27-25725
Mercury	650	65	2-Stroke	1964–1966	27-25725
Mercury	450 (4 CYL.)	45	2-Stroke	1956–1957	27-25725	Engine S/N 1476510 Thru 1531568
Mercury	500	50	2-Stroke	1957–1975	27-25725	Engine S/N 1421113 Thru 1755548
Mercury	650 (4 CYL.)	65	2-Stroke	1957–1964	27-25725	Engine S/N 1542745 Thru 2309310
Mercury	MARK 35A	35	2-Stroke	All	27-25725
Mercury	300 350	30-35	2-Stroke	1960–1961	27-25725	Engine S/N 1271884 Thru 1448139
Mercury	MARK 30, 30E	30	2-Stroke	All	27-25725
Mercury	MARK 30H, 55H	30-40	2-Stroke	All	27-25725
Mercury	MARK 55, 55E	40	2-Stroke	All	27-25725
Mercury	MARK 55AE, 55AM, 58AE, 58E	40-45	2-Stroke	All	27-25725
Mercury	400	40	2-Stroke	1957–1957	27-25725	S/N 1279685 Thru 1476509

Technical Specs

Product Type: Gasket
Installation: Magneto End Cap Cover
Weight: 0.01 kg (0.02 lbs)
Dimensions: 12.5 cm L x 10.5 cm W x 0.1 cm H
Technical Note: Designed to ensure a tight seal and reliable performance.

What’s in the Box

1 x Gasket (Replaces 27-25725)

Installation Notes

Ensure the engine is off, cool, and disconnected from the power source.
Locate and carefully remove the magneto end cap cover.
Take off the old gasket and thoroughly clean any residue from both mating surfaces. A clean surface is critical for a good seal.
Position the new gasket correctly onto the engine housing.
Re-install the end cap cover, ensuring it is aligned properly with the gasket.
Tighten the cover fasteners evenly in a crisscross pattern to the manufacturer's recommended torque specifications to avoid warping.

Troubleshooting & FAQ

How do I confirm this gasket is correct for my Mercury engine?

This gasket fits a broad range of vintage Mercury models. The best way to confirm fitment is to check the Engine & Model Compatibility table on this page. If your model is listed, pay close attention to any specified year ranges or engine serial numbers for an exact match.

What are the symptoms of a bad magneto end cap gasket?

A failed or worn-out gasket can lead to a poor seal, potentially allowing moisture or debris into the magneto assembly. This can cause ignition problems, rough running, or stalling. Visual inspection may reveal cracking, brittleness, or physical damage to the old gasket.

When should this gasket be replaced?

It is good practice to replace this gasket whenever the magneto end cap cover is removed for service or inspection. Gaskets compress over time and may not provide an adequate seal if reused.

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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