42878A2 42878C2 Mercury Exhaust Cover Plate | Genuine Used Part
42878A2 42878C2 Mercury Exhaust Cover Plate | Genuine Used Part
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🔧 Product Description
Genuine Mercury Exhaust Manifold Cover and Plate Assembly - Part Number: 42878A2
A genuine Mercury exhaust-manifold cover for selected 65HP to 90HP three-cylinder carburetted two-stroke outboards.
The service assembly is identified as 42878A2. The number 42878C2 is typically a casting or production identifier found on the physical cover and should not be treated as a separate service-kit number.
The cover works with baffle plate 428791 and gasket 43004009 to close and seal the water-cooled exhaust section of the powerhead.
⚙️ Key Features
- Genuine Mercury exhaust-manifold cover
- Correct service part number 42878A2
- Related casting reference 42878C2
- Includes or supports the internal exhaust baffle plate
- Designed for Mercury three-cylinder two-stroke powerheads
🚤 Compatibility
Commonly used on
- Mercury and Mariner three-cylinder induction and exhaust assemblies
Typically suits
- Engine models:
- Mercury 65 Jet
- Mercury 70HP three-cylinder
- Mercury 75HP three-cylinder
- Mercury 80HP three-cylinder
- Mercury 90HP three-cylinder
- Selected 75HP engines in serial range 0B240451-0C221999
- Later carburetted 65HP-90HP three-cylinder models using cover 42878A2
- HP Range: Approximately 65HP - 90HP
- Engine Type: Mercury / Mariner three-cylinder carburetted two-stroke outboard
- Year Range: Approximately late 1980s-early 2000s, dependent on serial number
🔌 Function
The cover seals the exhaust-water jacket against the cylinder block. The internal baffle directs cooling water around the exhaust passages while keeping the exhaust and cooling circuits correctly separated.
⚠️ Common Signs of Failure
- Cooling water leaks around the cover
- Exhaust staining appears at the gasket joint
- Internal corrosion damages the baffle or cover
- Cover is warped from overheating
- Mounting bolts seize or break in the cylinder block
🔄 Supersession & Cross Reference
OEM Supersession Chain
- 42878A2 → Supersedes 42878A1
- 42878A1 → Related to 42878T
- 42878A2 → Supersedes original cover 428781
- 42878C2 casting or production identifier
OEM / Related Numbers
- 42878A2
- 42878A1
- 42878T
- 428781
- 42878C2
- 428791 exhaust baffle plate
- 43004009 baffle-plate gasket
- 43004A99 related powerhead gasket set
- 82127335 cover retaining screw
Aftermarket / Verified Equivalents
- Aftermarket powerhead and exhaust-cover gasket sets replacing 43004009
- Specialist used 42878A2 / 42878T cover assemblies
- Reconditioned cover and baffle-plate assemblies
- No direct aftermarket cover casting
📦 Condition
- Genuine used part
- Supplied with the baffle plate only where fitted or stated
- Removed from running engine where applicable
- In good working condition unless otherwise stated
Shipping & Delivery
Shipping & Delivery
Flat-rate shipping Australia-wide — $14.99 per order, no matter how many parts you add. Orders dispatch from our Kadina, South Australia store. Need it urgently or want to collect in person? Call us on 0412 532 984 before ordering.
Returns & Warranty
Returns & Warranty
14-day change-of-mind returns — if it's not right or you ordered the wrong part, send it back within 14 days in the condition you received it for a refund or exchange. Full details in our Refunds & Returns policy.
Not sure this fits?
Not sure this fits?
Ask us before you buy — we check part numbers and fitment every day. Call 0412 532 984 (Mon–Fri 8.30am–4.30pm) or message us through the contact page with your engine or vehicle details.
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