Sierra Timer Base 18-99455 for Johnson Evinrude 3-Cylinder Outboard Engines

The Sierra 18-99455 timer base is an ignition system component built for Johnson and Evinrude 3 cylinder outboard engines. The timer base is the rotating ignition timing element that works with the distributor/trigger assembly to control spark timing across the cylinders, and it is a common wear or failure point in older Johnson/Evinrude ignition systems, especially when an engine develops intermittent spark, poor idle, or hard-starting symptoms. Replacing a worn or cracked timer base restores correct ignition timing and helps the engine run smoothly across the rev range.

This timer base is designed as a direct fit for 3 cylinder Johnson and Evinrude outboard powerheads, making it a straightforward service part for technicians and DIY boat owners performing ignition system maintenance or troubleshooting a no-spark condition. It ships as a standalone timer base component ready to install in place of the original unit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99455
• Application: Johnson Evinrude 3 Cylinder outboard engines
• Component Type: Ignition timer base
• Weight: 0.8 pounds
• UPC: 808282395377

Fitment

Fits Johnson and Evinrude 3 cylinder outboard engines.

Frequently Asked Questions

What engines does the Sierra 18-99455 timer base fit? The Sierra 18-99455 timer base is designed for Johnson and Evinrude 3 cylinder outboard engines.

What does a timer base do in an outboard ignition system? The timer base rotates to control ignition timing across the cylinders, working with the engine's distributor or trigger assembly to fire the spark at the correct point in each cylinder's cycle.

How much does the 18-99455 timer base weigh? It weighs 0.8 pounds.

What are signs that a timer base needs to be replaced? Intermittent spark, hard starting, rough idle, or inconsistent ignition timing on a Johnson or Evinrude 3 cylinder engine can point to a worn or cracked timer base like the Sierra 18-99455.

Is the Sierra 18-99455 a direct-fit replacement part? Yes, the Sierra 18-99455 timer base is built to fit in place of the original timer base on applicable Johnson Evinrude 3 cylinder outboards.

Does the Sierra 18-99455 include mounting hardware or other ignition parts? The Sierra 18-99455 is supplied as the timer base component itself; it does not include a distributor cap, points, or trigger assembly.

Can this timer base be used on 4 or 6 cylinder Johnson Evinrude engines? No, the Sierra 18-99455 is specified for 3 cylinder Johnson and Evinrude outboard engines only.

Is Sierra a trusted brand for outboard ignition parts? Sierra is a long-established manufacturer of marine engine parts, and the 18-99455 timer base is one of its ignition components for Johnson Evinrude 3 cylinder outboards.

What UPC is associated with the Sierra 18-99455 timer base? The UPC for the Sierra 18-99455 timer base is 808282395377.

Why would a timer base cause an outboard to run poorly on only some cylinders? Because the timer base coordinates spark timing to each cylinder in sequence, a worn or damaged unit like the one the Sierra 18-99455 replaces can cause uneven firing and rough running on a 3 cylinder Johnson or Evinrude engine.