Volvo Penta 3847640 Water-Cooled Exhaust Manifold – 8.1L Big-Block V8

Volvo Penta 3847640 – Water-Cooled Center-Rise Exhaust Manifold

What This Part Does

The 3847640 collects exhaust gases from the cylinder bank and routes them overboard while raw water circulates through the surrounding water jacket to manage exhaust temperature. It mounts to either the port or starboard cylinder head on compatible 8.1L big-block Volvo Penta engines.

Compatible Applications

• Volvo Penta 8.1Gi – Series A, B, C, D
• Volvo Penta 8.1GXi – Series A, B, C, D
• Volvo Penta 8.1GiI
• Volvo Penta 8.1GXiI
• Selected 8.2L and DPX big-block applications – verify via cross-reference catalog

⚠ Serial Number Fitment Notice: Volvo Penta used several different manifold and riser combinations across its big-block gasoline engines. Displacement alone is not sufficient for fitment — confirm your exact engine model and serial number before ordering.

When to Replace

Inspect and replace this manifold if you find any of the following:

• Internal corrosion or restricted water passages
• External rust-through or cracking
• Exhaust or water leakage at the manifold joints
• Water entering the exhaust ports

Marine exhaust manifolds are especially vulnerable on saltwater-operated engines where heat and corrosion act continuously. Regular inspection is strongly recommended as part of annual service.

Installation – Commonly Serviced Parts

Replace the manifold gasket and inspect the riser, water fittings, drain plug, and sealing surfaces at installation. Related service parts for 8.1L applications (sold separately):

• Manifold Gasket – 3852472
• Adapter – 21238201
• Riser Gasket – 3863191
• Exhaust Elbow – 3863189
• Brass Nipple – 3861159
• Brass Plug – 3595390
• Drain Plug – 21114522

These components are not included with the manifold.

Superseded Part Numbers

• Current: 3847640
• Replaces: 3860855
• Earlier related: 3852362, 3861459

Parts Desk Insights

Best Use Case: This is the correct center-rise water-cooled manifold for Volvo Penta 8.1L big-block V8 engines (Gi/GXi series). It fits port or starboard, making it a universal manifold for a single-engine or twin-engine 8.1L application.

Common Customer Issues: This part is occasionally confused with manifolds from the older AQ125/AQ145/AQ170 small-block series — those are not compatible. Always verify the engine model and serial number. On engines with high hours or saltwater exposure, we recommend inspecting or replacing the exhaust elbow (3863189) and riser gasket (3863191) at the same time to avoid a second disassembly.