Sierra RF Suppression Spark Plug Wire Set 18-99255 for Mercury Outboard Engines

The Sierra 18-99255 is an RF suppression spark plug wire set built for Mercury outboard engines. RF suppression wiring is designed to reduce radio frequency interference generated by the ignition system, which helps prevent static and interference with onboard electronics such as VHF radios, fish finders, and GPS units. This wire set is intended as a direct replacement for worn, cracked, or deteriorated factory plug wires, which can cause misfires, hard starting, and reduced engine performance if left in service too long. Keeping plug wires in good condition helps maintain a consistent spark path from the ignition coil to each spark plug, supporting reliable ignition timing and smoother engine operation. As part of Sierra's Mercury outboard engine parts line, the 18-99255 is manufactured to work with the electrical demands of a marine ignition system, which is exposed to more vibration, heat, and moisture than an automotive application. Replacing plug wires as a set, rather than individually, helps ensure consistent resistance and RF suppression performance across all cylinders. This product ships at 0.7 pounds.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99255
• Product Category: Mercury Outboard Spark Plug Wires
• Function: RF Suppression
• Weight: 0.7 pounds
• UPC: 808282395001

Frequently Asked Questions

What is the Sierra 18-99255 used for? The Sierra 18-99255 is an RF suppression spark plug wire set used to deliver ignition spark to Mercury outboard engine cylinders while reducing radio frequency interference from the ignition system.

Does this wire set fit Mercury outboard engines? Yes, the Sierra 18-99255 is categorized as a Mercury outboard spark plug wire set.

What does RF suppression mean on a spark plug wire? RF suppression means the wire is constructed to limit the radio frequency interference an ignition system generates, which helps reduce static and interference with onboard electronics like VHF radios and fish finders.

How much does the Sierra 18-99255 weigh? The Sierra 18-99255 RF suppression plug wire set weighs 0.7 pounds.

Is the Sierra 18-99255 a full wire set or a single wire? The Sierra 18-99255 is listed and sold as a plug wire set rather than a single wire.

Why replace plug wires instead of just the spark plugs? Plug wires deteriorate over time from heat, vibration, and moisture exposure, and worn wires can cause misfires or hard starting even with new spark plugs installed, which is why the Sierra 18-99255 set is offered as a complete wire replacement.

Is the Sierra 18-99255 genuine Sierra brand? Yes, part number 18-99255 is manufactured under the Sierra brand.

What is the UPC for the Sierra 18-99255? The UPC for the Sierra 18-99255 RF suppression plug wire set is 808282395001.

Can worn plug wires affect marine electronics? Yes, deteriorated plug wires without adequate RF suppression can generate interference that affects nearby marine electronics, which is part of why the Sierra 18-99255 is built as an RF suppression wire set.

Should all plug wires be replaced at the same time? Replacing the full set at once, such as with the Sierra 18-99255, helps ensure consistent resistance and RF suppression performance across all engine cylinders rather than mixing old and new wires.