Description

The Sierra 18-5443 is a marine ignition coil used in select Mercury, MerCruiser, OMC, Volvo Penta, and Crusader applications. Current cross-reference listings identify it as replacing Mercury 817378, 817378T, and 898253T27, along with OMC 3854002 and Volvo Penta 3854002-7.

This coil is commonly described for Delco EST / HEI-style ignition and high-performance applications, with current Sierra-linked fitment references centered on inboard and sterndrive engine families, not general 2-stroke outboard use.

Key Features

• Sierra part number: 18-5443
• Marine ignition coil
• Replaces Mercury 817378 / 817378T / 898253T27
• Replaces OMC 3854002
• Replaces Volvo Penta 3854002-7
• Commonly listed for Delco EST / HEI ignition applications

Engine Compatibility
Current fitment references support applications including 3.0L (1991 and newer), 5.7 EFI (1996 and newer), and 7.4 EFI (1995 and newer), with additional listings broadly describing fitment for late-model GM marine engines with Delco EST distributors. Fitment should be confirmed by exact engine model and serial number before ordering.

Serial Number Fitment Notice
Fitment should be verified using the engine model and serial number, along with the existing coil’s OEM number. Matching by Sierra 18-5443 or the supported OEM cross-reference number is the safest method.

When This Part Needs Replacement
Replace the ignition coil if there is weak or intermittent spark, hard starting, misfire under load, or confirmed coil failure during ignition-system testing. This guidance is based on the function of the part; the cited sources mainly confirm identity and fitment.

Installation Notes
Install only where 18-5443 or the matching OEM cross-reference is specified. Confirm ignition-system type and engine application before installation.

Alternate / Superseded Part Numbers when applicable

• 18-5443
• 817378
• 817378T
• 898253T27
• 3854002
• 3854002-7
• 7243200

Parts Desk Insight
The most important thing on 18-5443 is matching the ignition system and engine family, not just the connector style. Current fitment support points to Delco EST / HEI-type marine engine applications, so serial-number confirmation matters before listing it against a specific engine.

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