Sierra 18-8803-2 MAGFORCE Spark Plug Wire Set, 8-Cylinder, Replaces Mercury Marine 84-816761A9, OMC 503755

The Sierra 18-8803-2 is a MAGFORCE ignition wire set built for 8-cylinder Mercury Marine and OMC engines. Sierra markets these as "Electronics Friendly," meaning the wire construction is engineered to protect onboard electronic devices and electronic engine controls from radio frequency interference (RFI) and electromagnetic interference (EMI) while still delivering maximum voltage to the spark plugs. Each wire uses a mag/wire wound core to suppress interference without sacrificing spark energy, paired with moisture-proof, molded distributor insulators that seal out water intrusion at the distributor cap connection. A high-quality conductive center carrier reinforcement maintains conductor integrity over time, and a high tensile strength outer membrane adds durability and heat resistance so the wires hold up in the engine bay.

The set is designed for exact-fit installation on the applicable engine, meaning the wires are sized and routed to match factory configuration without cutting or custom fitting. This is a complete 8-cylinder wire set, replacing the full run of factory or worn ignition wires in one kit. It is built to meet or exceed original equipment quality and is a direct fit replacement referencing multiple Mercury Marine and OMC OEM part numbers.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-8803-2
• Product Name: Wire Set
• Cylinder Count: 8
• Material: Copper (core), PVC (insulation)
• Wire Diameter: 8 millimeters
• Connector Type: Other
• Weight: 2.17 pounds
• UPC: 808282194925
• Included Components: Wiring, Plug Set
• Fit Type: Universal Fit

Fitment

Fits Mercury Marine and OMC 8-cylinder engines using the OEM part numbers listed below.

Replaces (OEM)

• Mallory 9-28000
• Mallory 9-28010
• Mallory 9-28012
• Mallory 9-28021
• Mercruiser 84-43376A9
• Mercury Marine 84-816761Q9
• Mercury Marine 84-816761A9
• Mercury Marine 84-813720A10
• Mercury Marine 84-813720A9
• Mercury Marine 84-816761Q10
• OMC 503752
• OMC 503755

Frequently Asked Questions

What engines does the Sierra 18-8803-2 wire set fit? The 18-8803-2 is built for 8-cylinder Mercury Marine and OMC engines, matching the factory OEM part numbers it cross-references.

How many spark plug wires are in this set? This kit is a complete 8-cylinder set, so it includes enough ignition wires to replace all eight spark plug leads on the engine in one purchase.

Which OEM part numbers does the 18-8803-2 replace? It cross-references Mercury Marine 84-816761Q9, 84-816761A9, 84-813720A10, 84-813720A9, and 84-816761Q10, Mercruiser 84-43376A9, OMC 503752 and 503755, and Mallory 9-28000, 9-28010, 9-28012, and 9-28021.

Is the Sierra 18-8803-2 the same quality as the original wires? Sierra manufactures this MAGFORCE wire set to meet or exceed original equipment quality, so it is built as a direct, exact-fit replacement rather than a generic substitute.

What are the wires made of? Each wire in the 18-8803-2 set uses a copper core with PVC insulation, plus a mag/wire wound core construction for interference suppression.

How thick are the spark plug wires? The wires in the Sierra 18-8803-2 set measure 8 millimeters in diameter.

Will these wires interfere with my boat's electronics? No. Sierra designed the MAGFORCE 18-8803-2 wire set to be Electronics Friendly, suppressing radio frequency interference (RFI) and electromagnetic interference (EMI) so it does not disrupt onboard electronic devices or engine controls.

How much does the 18-8803-2 wire set weigh? The complete Sierra 18-8803-2 ignition wire set weighs 2.17 pounds.

Does the wire set include the distributor cap insulators? Yes, the 18-8803-2 set uses moisture-proof, molded distributor insulators to keep water out of the distributor cap connections.

Why do the wires use a wound core instead of solid copper throughout? The mag/wire wound core in the 18-8803-2 set is designed to deliver maximum voltage to the spark plugs while still suppressing RFI and EMI, which a plain solid conductor would not filter out as effectively.

Is installation straightforward? Sierra designs the 18-8803-2 as an exact-fit wire set, so it installs using the factory routing and connections without custom cutting or fitting.

What is included in the box? The Sierra 18-8803-2 comes as a complete 8-cylinder wiring and plug set ready to install on Mercury Marine and OMC engines.