Mercury / Quicksilver 27-8079821 2BBL Carburetor Base Gasket | MerCruiser 3.0L / 4.3L / 5.0L / 5.7L
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Part Details
- Part Number: 27-8079821 (base number: 8079821)
- Brand: Mercury Marine / Quicksilver (Genuine OEM)
- Official Product Type: 2-Barrel Carburetor Base Mounting Gasket
- Carburetor Fit: Rochester 2BBL and MerCarb 2BBL
- System: Fuel system — carburetor-to-intake mounting
- Dimensions: 4.88 in. L × 3.00 in. W × 0.13 in. thick
- Weight: 23 g / 0.05 lb
- Supersedes: 27-807982, 807982, 27-70143, 27-701431, 27-807982B, 27-70143B1
- Sierra Aftermarket Cross-Reference: 18-0994-9
- GLM Aftermarket Cross-Reference: 32180
- GTIN / UPC: 745061491397
What This Part Is
Mercury / Quicksilver 27-8079821 is a genuine OEM carburetor base mounting gasket that seals the base of the 2-barrel Rochester or MerCarb carburetor to the intake manifold or mounting surface. It prevents vacuum leaks and unmetered air from entering below the carburetor. Mercury parts diagrams show this gasket positioned directly beneath the carburetor on applicable 3.0L, 4.3L, and 5.7L carbureted engine configurations.
Important: This is the 2-barrel carburetor base gasket, not a general intake manifold gasket. It is specific to Rochester and MerCarb 2BBL carburetor installations. Confirm the carburetor type and engine serial number before ordering.
Compatible Applications
Fitment must be confirmed by engine model, serial number, and carburetor type. Documented MerCruiser applications include:
- MerCruiser 3.0L / 181 CID inline-4 — carbureted (Rochester / MerCarb 2BBL)
- MerCruiser 4.3L / 262 CID V6 — 2-barrel carbureted configurations (4.3LX Gen+ 2BBL and related)
- MerCruiser 5.0L / 305 CID V8 — 2-barrel carbureted Alpha/Bravo configurations
- MerCruiser 5.7L / 350 CID V8 — 2-barrel carbureted Alpha/Bravo configurations
- Other MerCruiser gasoline engines where the fuel-system diagram specifically calls for 8079821
The same 4.3L, 5.0L, and 5.7L engine families were also produced with 4-barrel carburetors, TBI, or EFI induction — those use different gaskets. Do not select by engine displacement alone; confirm the carburetor type first.
When to Replace
Replace the carburetor base gasket whenever the carburetor is removed, or if any of the following are present:
- Vacuum leakage or air hissing at the carburetor base
- Unstable, rough, or high idle that cannot be corrected by adjustment
- Lean running condition or hesitation under load
- Cracked, crushed, or hardened gasket material
- Fuel staining or weeping around the carburetor mounting flange
Reusing a compressed carburetor base gasket can create an intake air leak that makes idle adjustment or carburetor tuning difficult to complete successfully. Always fit a new gasket when the carburetor is removed.
Service Interval
Replace at every carburetor removal — during rebuild, cleaning, or any service that requires lifting the carburetor off the manifold. The gasket is a low-cost item and should not be reused once removed from service.
Installation Notes
- Remove all old gasket material from the carburetor base and intake manifold flange before fitting the new gasket
- Inspect both mating surfaces for warping, cracks, or damage
- Confirm the gasket openings align correctly with the throttle bores and mounting stud pattern
- On documented 3.0L applications the carburetor is retained by four studs — tighten fasteners evenly to the torque specified in the applicable MerCruiser service procedure
- After startup, inspect for vacuum or fuel leakage at the carburetor base and recheck idle quality
Technical FAQ
Does this gasket fit 4-barrel, TBI, or EFI MerCruiser engines?
No. 27-8079821 is specific to Rochester and MerCarb 2-barrel carburetor installations. Engines equipped with 4-barrel carburetors, throttle-body injection, or multi-port EFI use different intake and carburetor gaskets. Confirm the induction system type before ordering.
Which part numbers does 27-8079821 replace?
27-8079821 is the current production number and supersedes 27-807982, 807982, 27-70143, 27-701431, 27-807982B, and 27-70143B1. Earlier listings may show the base number 8079821 without the Mercury prefix.
What aftermarket part numbers cross-reference to 27-8079821?
Sierra 18-0994-9 and GLM 32180 are documented aftermarket equivalents. Always verify the cross-reference against the current OEM diagram for your engine before substituting.
Can I reuse the old gasket if it looks intact?
Mercury and MerCruiser service procedures call for a new gasket at every carburetor removal. Even a gasket that appears intact has been compressed to the specific surface finish of the original mating parts — it will not seal as reliably when reinstalled and may cause a vacuum leak.
Superseded / Cross-Reference Part Numbers
- Current Mercury OEM: 27-8079821 / 8079821
- Earlier Mercury references: 27-807982, 807982, 27-70143, 27-701431, 27-807982B, 27-70143B1
- Sierra aftermarket: 18-0994-9
- GLM aftermarket: 32180
- Aftermarket reference: MC47-27-70143
- GTIN / UPC: 745061491397
Related Parts
- Browse Marine Gaskets, Seals & O-Rings for all carburetor and intake sealing components
- Browse Fuel & Air Systems for carburetors, fuel pumps, and fuel system service parts
- Browse MerCruiser Marine Engine Parts
Parts Desk Insights
Best use case: 27-8079821 is a routine consumable for any carbureted MerCruiser service — keep one on hand any time a Rochester or MerCarb 2BBL carburetor is being removed for cleaning, rebuilding, or adjustment. At this price point it is not worth removing a carburetor twice because of a skipped gasket.
Common issue: The most frequent mistake is ordering this gasket for an engine that has a 4-barrel carburetor, TBI, or EFI — the 2BBL base pattern does not match those configurations. The second common issue is reusing the old gasket to save a step during a service call, then having to return the boat for an idle complaint caused by a base vacuum leak. Always fit a new gasket when the carburetor comes off.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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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.
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