Sierra Ignition Pack 18-99304 for Yamaha 3 Cylinder 50 HP 1984-1988 2-Stroke Outboards, Replaces 6H4-85540-20-00

The Sierra 18-99304 Ignition Pack is a replacement ignition control module built for Yamaha 3 cylinder 50 HP 2-stroke outboard motors, 1984-1988, all models. The ignition pack manages spark timing and delivery to the engine's cylinders, and is a common wear item on outboards of this age as internal components degrade with heat cycling and vibration over years of service. Installing a fresh unit restores reliable spark output, helping resolve hard starting, rough idle, misfires, or a complete no-spark condition traced to the ignition pack itself.

This part is sold under Sierra part number 18-99304 and is built to meet or exceed the output and durability of the original Yamaha ignition pack it replaces. It mounts in the same location as the factory unit and uses the same electrical connections, so installation follows the same steps as removing and replacing the original ignition pack.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99304
• Category: Yamaha Outboard Ignition System
• Weight: 0.9 pounds
• UPC: 808282396084
• Cylinders: 3

Fitment

• Yamaha 3 Cylinder 50 HP, 1984-1988, 2-Stroke, All Models

Replaces (OEM)

• 6H4-85540-20-00
• 6H4-85540-21-00

Frequently Asked Questions

What does the Sierra 18-99304 ignition pack fit? It fits Yamaha 3 cylinder 50 HP outboard motors, 1984-1988, 2-stroke, all models.

Is the Sierra 18-99304 an OEM part or an aftermarket replacement? The 18-99304 is an aftermarket ignition pack built to replace the original Yamaha ignition pack, not an OEM Yamaha part.

Which OEM part numbers does the 18-99304 replace? The Sierra 18-99304 ignition pack replaces Yamaha OEM numbers 6H4-85540-20-00 and 6H4-85540-21-00.

How much does this ignition pack weigh? The Sierra 18-99304 ignition pack weighs 0.9 pounds.

What symptoms indicate my ignition pack needs replacement? Hard starting, rough idle, engine misfire, or a complete loss of spark on a Yamaha 3 cylinder 50 HP 2-stroke outboard can indicate a failing ignition pack, which the 18-99304 is designed to replace.

Does the 18-99304 work on 4-stroke Yamaha 50 HP engines? No, the 18-99304 is built for the Yamaha 3 cylinder 50 HP 2-stroke outboard, 1984-1988, all models.

What is included when I order the 18-99304? The order includes one Sierra 18-99304 ignition pack for the Yamaha 3 cylinder 50 HP 2-stroke outboard.

Does installing the 18-99304 require special tools? Installation follows the same mounting location and electrical connections as the original Yamaha ignition pack it replaces, so no specialized tools beyond standard hand tools are needed.

Can I use the 18-99304 on a different horsepower Yamaha outboard? The 18-99304 is specified for the Yamaha 3 cylinder 50 HP 2-stroke outboard, 1984-1988, all models, so it should be matched to that engine.

Is the Sierra 18-99304 a direct fit replacement? Yes, the 18-99304 is designed as a direct replacement for the Yamaha ignition pack carrying OEM numbers 6H4-85540-20-00 and 6H4-85540-21-00.