Mercury MerCruiser Head Gasket 27-342731
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The Mercury MerCruiser Quicksilver 27-342731 Head Gasket is an OEM-style replacement head gasket for early MerCruiser inline 4-cylinder engines. It fits MCM 110, MCM 120, and 2.5L MerCruiser applications from 1963–1989, helping seal the cylinder head to the engine block during top-end service.
Key Features
- Head gasket for select early MerCruiser 4-cylinder engines
- Fits MCM 110, MCM 120, and 2.5L
- Application range: 1963–1989
- Used when servicing or reinstalling the cylinder head
- Helps seal combustion pressure, coolant passages, and oil passages
- Supersedes 27-34273
- Current part number: 27-342731
Engine Compatibility
Fits:
- MerCruiser MCM 110
- MerCruiser MCM 120
- MerCruiser 2.5L
- Model years: 1963–1989
Serial Number Fitment Notice
Fitment should still be confirmed by engine serial number and parts diagram, especially on older MerCruiser engines where prior repowers, block changes, or cylinder-head changes may affect gasket selection.
When This Part Needs Replacement
Replace this head gasket during cylinder-head removal, head resurfacing, valve service, overheating repairs, coolant-in-cylinder diagnosis, compression loss, or any top-end repair where the original head gasket has been disturbed.
Installation Notes
Inspect the cylinder head and block deck for warpage, corrosion, and surface damage before installation. Clean all mating surfaces carefully, follow the proper MerCruiser torque sequence, and use the correct service manual torque specifications for the engine.
Alternate/Superseded Part Numbers
- 27-342731
- Supersedes 27-34273
Parts Desk Insight
Older MerCruiser 110/120/2.5L engines can have decades of service history behind them, so matching by engine family alone is not always enough. Serial-number and parts-diagram confirmation is still the safest way to make sure the head gasket matches the actual block and cylinder head on the boat.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.