Gasket Set – Fits Mercury/Mariner 90-150HP 6-Cylinder Engines (Replaces 27-85653A87)

$89.54 $143.00

Shipping calculated at checkout.

Gasket Set – Fits Mercury/Mariner 90-150HP 6-Cylinder Engines (Replaces 27-85653A87) is backordered and will ship as soon as it is back in stock.

Worry-free returns

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 complete Gasket Set – Fits Mercury/Mariner 90-150HP 6-Cylinder Engines provides all necessary seals for a full powerhead rebuild. It is designed for Mercury and Mariner 2-stroke, 6-cylinder inline engines manufactured between 1974 and 1988, ensuring a precise, factory-level fit and seal.

This kit serves as a direct replacement for Mercury OEM part number 27-85653A87 and interchanges with earlier numbers including 27-85653A32, 27-85653A79, 27-60476A75, 27-60476A74, 27-60476A73, 27-60476A72, and GLM 39550.

Product Type: Powerhead Gasket Set
Installation: Engine-specific for a direct fit.
Materials: Includes various gaskets made from high-quality paper, rubber, and metal composites.

Part Number Matrix

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

Brand	Part Number
Mercury	27-85653A87
Mercury	27-85653A32
Mercury	27-85653A79
Mercury	27-60476A75
Mercury	27-60476A74
Mercury	27-60476A73
Mercury	27-60476A72
GLM	39550

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury models, check your engine’s serial number against the notes provided to ensure an exact match.

For Mariner models, this kit fits specific models from 1978 to 1980. Verify your serial number where applicable.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	90 EL	90	2-Stroke	1978–1985	27-85653A87	Serial 4845301-5299505, 1090528, 1090529, 1090520, 1090522, 1090523
Mercury	90 ELPT	90	2-Stroke	1978–1985	27-85653A87	Serial 4845301-5299505, 1090628, 1090629, 1090620, 1090622, 1090623
Mercury	115 EL	115	2-Stroke	1975–1988	27-85653A87	Serial 3525441-4855152, 1115526, 1115527, 1115528, 1115529, 1115520, 1115522, 1115525
Mercury	115 ELPT	115	2-Stroke	1975–1988	27-85653A87	Serial 3525441-4855152, 1115626, 1115627, 1115628, 1115629, 1115620, 1115622, 1115623, 1115625
Mercury	115 EXLPT	115	2-Stroke	1978–1983	27-85653A87	Serial 1115648, 1115649, 1115640, 1115642, 1115643
Mercury	140 EL	140	2-Stroke	1978–1981	27-85653A87	Serial 3293234-3502805, 1140528, 1140529, 1140520
Mercury	140 ELPT	140	2-Stroke	1978–1981	27-85653A87	Serial 3293234-3502805, 1140628, 1140629, 1140620
Mercury	150	150	2-Stroke	1974–1978	27-85653A87	Serial 3502806-4868997, 1150505, 1150506, 1150507
Mercury	150 EL	150	2-Stroke	1975–1985	27-85653A87	Serial 1150526, 1150527, 1150525
Mercury	150 ELPT	150	2-Stroke	1975–1985	27-85653A87	Serial 1150626, 1150627, 1150625
Mercury	150 XS	150	2-Stroke	1977	27-85653A87	Serial 1150537
Mariner	90 EL	90	2-Stroke	1979–1980	27-85653A87	Serial 7090529, 7090520
Mariner	90 ELPT	90	2-Stroke	1979–1980	27-85653A87	Serial 7090629, 7090620
Mariner	115 EL	115	2-Stroke	1978–1980	27-85653A87	Serial 7115528, 7115529, 7115520
Mariner	115 ELPT	115	2-Stroke	1978–1980	27-85653A87	Serial 7115628, 7115629, 7115620
Mariner	115 EXLPT	115	2-Stroke	1980	27-85653A87	Serial 7115640
Mariner	140	140	2-Stroke	1978–1979	27-85653A87	Serial 7140528, 7140529
Mariner	140 ELPT	140	2-Stroke	1978–1979	27-85653A87	Serial 7140628, 7140629

Technical Specs

Product Type: Powerhead Gasket Set
Installation: Engine-specific
Housing Material: Various (paper, rubber, metal)
Product Dimensions: 57.5 cm × 30.0 cm × 1.5 cm
Weight: 1.13 kg (2.49 lb)

What’s in the Box

1 x Complete Gasket Set (Replaces 27-85653A87)

Installation Notes

Disconnect the battery and all electrical connections to the engine.
Drain the engine coolant and oil completely.
Remove any external components obstructing access to the powerhead, such as the flywheel cover, carburetors, and electrical plates.
Carefully loosen and remove the powerhead mounting bolts in the sequence specified by the manufacturer's service manual.
Lift the powerhead off the engine midsection. Be careful not to damage any remaining connected components.
Remove all old gasket material from the mating surfaces of the cylinder block and crankcase cover. Use a plastic scraper to avoid gouging the aluminum.
Wipe the surfaces clean with a suitable solvent.
Position the new gaskets correctly on the clean, dry surfaces. Ensure all bolt holes and passages align perfectly.
Carefully lower the powerhead back into position.
Install the bolts and torque them to the manufacturer's specified values and sequence using a calibrated torque wrench.
Reinstall all previously removed components, reconnect electrical systems, and refill fluids.
Before starting, check for leaks and verify all components are secure. Start the engine and let it warm up, monitoring for leaks or unusual noises.

Troubleshooting & FAQ

How do I know if this gasket set is correct for my engine?

This set is designed for specific Mercury and Mariner 6-cylinder inline engines from 1974–1988. The most reliable way to confirm fitment is by matching your engine's model and serial number to our compatibility table. Also, verify that your existing part number is listed in our Part Number Matrix.

What are the common signs of a failing powerhead gasket?

Symptoms of a blown powerhead gasket include water in the cylinders (leading to difficult starting or hydrolock), milky or discolored oil, engine overheating, loss of compression in one or more cylinders, and visible water or exhaust leaks from the mating surfaces.

Can I reuse any of my old gaskets?

No. Gaskets are designed for single-use only. They crush and deform to create a seal and will not provide a reliable seal if reused. Always replace all gaskets during a powerhead service.

Do I need sealant with these gaskets?

Most gaskets in this kit are designed to be installed dry. However, always refer to your engine's specific service manual. Some applications may require a thin layer of a specific type of sealant on certain gaskets.

What is the most critical part of the installation process?

Proper surface preparation and correct torque sequence are both critical. Mating surfaces must be perfectly clean and flat. Bolts must be tightened in the specified pattern and to the exact torque value to ensure even pressure and a lasting seal.

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.

Payment & Security

Payment methods

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.