Mercury Marine Block Cover Gasket - Fits Mercury/Mercruiser 40-45 HP Outboards (Replaces 27-437772)

$29.37

Shipping calculated at checkout.

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 is a direct replacement Mercury Marine Block Cover Gasket designed for select Mercury and Mercruiser 40-45 HP 4-cylinder outboard engines and 30 HP Jet models produced from the late 1980s through the early 2000s. It provides a reliable seal for the engine block cover, preventing coolant and water leaks.

This part is a direct replacement for Mercury OEM part numbers 27-437772, 27-437771, 27-96483, and 27-43777.

Engineered as a direct replacement for a perfect fit.
Constructed from high-quality, OEM-specified gasket material.
Meets factory original equipment part standards for performance and durability.

Part Number Matrix

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

Brand	Part Number	Notes
Mercury	27-437772	Current
Mercury	27-437771	Superseded by 27-437772
Mercury	27-96483	Superseded by 27-437771
Mercury	27-43777	Superseded part

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury and Mercruiser engines, compatibility is determined by the serial number. Please verify that your engine's serial number falls within the ranges listed in the table.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Mercury	45 (4 CYL.)	45	4-Stroke	0A719281 & Up	27-437772
Mercury	45 (4 CYL.)	45	4-Stroke	0B110789 & Up	27-437772
Mercury	45 (4 CYL.)	45	4-Stroke	9466692 & Up	27-437772
Mercury	40 (4 CYL.)	40	4-Stroke	0C159200 & Up	27-437772
Mercury	40 (4 CYL.)	40	4-Stroke	9570790 & Up	27-437772
Mercury	40 JET	40	4-Stroke	0C159200 THRU 0G589999	27-437772
Mercury	30 JET	30	4-Stroke	9570790 & Up	27-437772

Technical Specs

Product Type: Block Cover Gasket
Installation: Direct replacement
Dimensions: 355.6mm × 177.8mm × 31.75mm (14.0" × 7.0" × 1.25")
Weight: 0.06 kg (0.13 lb)
Material: OEM specified gasket material

What’s in the Box

1 x GASKET (27-437772)

Installation Notes

Ensure the engine is off and cool to the touch. Disconnect the negative battery terminal.
If necessary, drain the engine block's cooling system to prevent spills.
Remove any components that obstruct access to the engine block cover.
Systematically loosen and remove the bolts securing the block cover.
Carefully detach the cover and the old gasket. Note the orientation of the cover.
Thoroughly clean both the engine block surface and the inside of the cover. Remove all traces of old gasket material, sealant, and debris.
Position the new gasket correctly onto the engine block.
Re-install the block cover, ensuring it is properly aligned with the gasket and bolt holes.
Hand-tighten the bolts, then torque them to the manufacturer's specifications in the recommended sequence.
Re-install any components that were removed.
Refill the cooling system if it was drained.
Reconnect the battery, start the engine, and carefully inspect for any leaks around the block cover.

Troubleshooting & FAQ

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

This gasket fits a range of Mercury/Mercruiser engines. The most accurate way to confirm fitment is to match your engine's serial number to the ranges provided in the "Engine & Model Compatibility" table. Do not rely on model year alone.

What are the common signs of a failing block cover gasket?

Signs of a bad gasket include visible water or coolant leaks from the side of the engine block, engine overheating, milky or discolored engine oil (indicating water contamination), or a loss of compression.

Should I use sealant or adhesive with this gasket?

Most modern gaskets, including this one, are designed to be installed dry without any additional sealant. Applying sealant can sometimes interfere with a proper seal. Always refer to your specific engine's service manual for the manufacturer's recommendation.

What's the difference between part number 27-437772 and the others listed?

Part number 27-437772 is the current, official OEM part number. The other numbers (27-437771, 27-96483, 27-43777) are older, superseded part numbers that have been replaced by 27-437772. They are all functionally equivalent.

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.