3978734CN Aftermarket Cummins Heat Exchanger 5 x 27 in | Sawley's Select Marine Parts

🔧 Product Description

Aftermarket replacement Engine Heat Exchanger - Replaces Part Number: 3978734CN

New heavy-duty copper-nickel replacement heat exchanger for Cummins 3978734. The assembly measures approximately 5 inches in diameter and 27 inches overall.

⚙️ Key Features

• Direct replacement for Cummins 3978734

• Approximately 5-inch diameter × 27-inch overall length

• Copper-nickel seawater tube bundle

• Heavy-duty marine closed-cooling construction

• Original-style mounting and hose layout

🧰 Kit / Assembly Contents

• 1 × Complete heat exchanger assembly - P/N 3978734CN

• 1 × integrated copper-nickel tube bundle

• End covers, seals, zincs and mounting hardware are renewed separately unless included

🔄 Supersession & Cross Reference

OEM Supersession Chain:

• 3978734CN → Copper-nickel replacement for Cummins 3978734

OEM / Related Numbers:

• 3978734

Aftermarket / Verified Equivalents:

• Mr Cool: MRC3978734CN

• Seakamp: 3978734CN

• Lenco: LE3978734

🚤 Compatibility

Commonly used on:

• Cummins marine diesel installations whose original heat exchanger is P/N 3978734

Typically suits:

• Engine / Equipment models:

• Cummins engine arrangements identified by OEM P/N 3978734 and matching 5-inch × 27-inch shell configuration

• Output / Engine Rating: Engine rating is arrangement-dependent

• Engine / System Type: Turbocharged Cummins marine diesel engine

• Year Range: Arrangement- and serial-dependent

• Serial / Model Identification: Confirm engine serial, CPL, hose diameters and mounting orientation.

🔌 Function

The heat exchanger transfers engine or generator coolant heat into the raw-water circuit while keeping the two fluids separated. This maintains the correct closed-circuit operating temperature and protects the engine from direct seawater circulation.

Common signs of failure:

• Engine or generator overheating under sustained load

• Coolant loss without an obvious external hose leak

• Saltwater and coolant cross-contamination

• Restricted raw-water discharge or uneven end-cap temperature

• Corrosion, green staining, cracked solder joints or pressure-test failure

📦 Condition

• New aftermarket replacement part

• Brand new

• Supplied in original or equivalent packaging