Sierra Ignition Coil 18-99321 for Johnson/Evinrude 3 and 4 Cylinder Outboards

The Sierra 18-99321 is an ignition coil built for Johnson and Evinrude outboard engines with 3 or 4 cylinder configurations. As a core component of the ignition system, the coil steps up battery voltage into the high-voltage pulse needed to fire the spark plugs, and a weak or failing coil is a common cause of hard starting, misfires, rough idle, or a no-spark condition on these outboards. This part is a bolt-on replacement, designed to install using the factory mounting points without modification.

The coil measures 4 x 3 x 3 inches and weighs 0.6 pounds. It is intended for marine personal watercraft and outboard applications where Johnson/Evinrude 3 or 4 cylinder ignition coils are specified. Installing a properly matched ignition coil helps restore consistent spark energy and reliable engine starting.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99321
• Product Type: Ignition Coil
• Compatible Engine: Johnson/Evinrude 3 or 4 Cylinder
• Installation Type: Bolt-On
• Item Dimensions: 4 x 3 x 3 inches
• Weight: 0.6 pounds
• Vehicle Service Type: Marine Personal Craft

Fitment

• Johnson/Evinrude outboard engines, 3 Cylinder
• Johnson/Evinrude outboard engines, 4 Cylinder

Frequently Asked Questions

What engines is the Sierra 18-99321 ignition coil designed for? The Sierra 18-99321 is designed for Johnson and Evinrude outboard engines with 3 or 4 cylinder configurations.

Is the 18-99321 a direct bolt-on replacement? Yes, the 18-99321 ignition coil uses a bolt-on installation type, so it mounts using the existing factory hardware points without modification.

What are the dimensions of this ignition coil? Sierra part 18-99321 measures 4 x 3 x 3 inches.

How much does the 18-99321 ignition coil weigh? It weighs 0.6 pounds.

What symptoms indicate my ignition coil needs replacement? Hard starting, engine misfire, rough idle, or a complete loss of spark on a Johnson/Evinrude 3 or 4 cylinder outboard are common signs that the ignition coil, such as the Sierra 18-99321, should be inspected and replaced.

Does the 18-99321 work on both 3 cylinder and 4 cylinder Johnson/Evinrude engines? Yes, the Sierra 18-99321 ignition coil is listed for both 3 cylinder and 4 cylinder Johnson/Evinrude outboard engines.

What is included when I order the 18-99321? The order includes one Sierra 18-99321 ignition coil, ready for bolt-on installation on a compatible Johnson/Evinrude outboard.

Is this ignition coil intended for personal watercraft or outboard boats? The 18-99321 is classified for marine personal craft service and is used on Johnson/Evinrude 3 or 4 cylinder outboard engines.

Can I install the Sierra 18-99321 myself? Because it is a bolt-on ignition coil, the 18-99321 can typically be installed with basic hand tools by removing the old coil and mounting the replacement in the same location, though buyers unfamiliar with marine ignition systems should have the installation checked by a qualified marine technician.

What material is the ignition coil housing made of? Material composition for the Sierra 18-99321 is not specified in the available product data.