MAR078 Aftermarket Mercruiser MCM V8 Big-Block Exhaust Manifold | Sawley's Select Marine Parts

🔧 Product Description

Aftermarket Mercruiser MCM V8 Big-Block Exhaust Manifold - Part Number: MAR078

A water-jacketed exhaust manifold for MerCruiser MCM big-block V8 engines. It replaces several 807078 and 89011 manifold numbers used on 330/340, 454 MAG, 7.4L and 8.2L engine families.

⚙️ Key Features

• For GM 454 and 502 CID big-block V8 engines

• Water-jacketed marine cast-iron manifold

• Matches the 807078 service family

• Suitable for port or starboard bank as specified by installation

• Use new manifold and elbow gaskets

🔄 Supersession & Cross Reference

OEM Supersession Chain:

• 807078T10 → Later reference in the 807078A2/A4/A6/Q07/T08/T09/T10 family

OEM / Related Numbers:

• MAR078

• 807078A2

• 807078A4

• 807078A6

• 807078Q07

• 807078T08

• 807078T09

• 807078T10

• 89011A8

Aftermarket / Verified Equivalents:

• Recmar: MAR078

• Sierra: 18-1957-2

• HGE: HGE9011 family

🚤 Compatibility

Commonly used on:

• MerCruiser MCM big-block V8 wet-exhaust systems

Typically suits:

• Engine models:

• MerCruiser 330

• MerCruiser 340 MIE

• MerCruiser 370 / 454 MAG

• MerCruiser 7.4L / 454 CID

• MerCruiser 8.2L / 502 CID

• Engine Displacement: 454 CID / 7.4L and 502 CID / 8.2L

• Approximate Application Years: 1987-1997

🔌 Function

The manifold collects exhaust from one V8 cylinder bank and cools the casting before the gas reaches the riser or elbow.

Common signs of failure:

• External exhaust or cooling-water leakage

• Internal water leakage into the exhaust ports or cylinders

• Restricted cooling passages or abnormal manifold temperature

• Cracked casting, warped flange or corroded sealing face

• Loss of power caused by an internally restricted exhaust passage

📦 Condition

• Brand new aftermarket replacement part

• New and unused

• Supplied in manufacturer or equivalent protective packaging