Sierra 18-99406 Timer Base, Replaces 763777, for Johnson/Evinrude 3 Cylinder 60-75 HP 1979-2001

The Sierra 18-99406 Timer Base is a direct-fit ignition component for Johnson and Evinrude 3 cylinder outboard engines, built to restore correct spark timing on units that have developed rough idle, misfiring, or hard-starting symptoms tied to a worn or failed timer base assembly. It mounts in place of the factory timer base and interfaces with the engine's ignition trigger system to maintain accurate timing across the RPM range.

This timer base is designed for 3 cylinder Johnson and Evinrude outboards rated at 60, 65, 70, and 75 horsepower covering the 1979-2001 production span, and it cross-references to a range of factory part numbers so it can replace an original timer base that has cracked, worn at the follower pin, or lost consistent contact with the timing components. Installers should confirm the horsepower and cylinder count of their specific engine before ordering, since timer bases are not interchangeable across different cylinder configurations.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99406
• UPC: 808282394370
• Product Dimensions: 8 x 5 x 3 inches
• Weight: 0.9 pounds
• Cylinder Count: 3 Cylinder
• Engine Horsepower: 60, 65, 70, 75 HP
• Fitment Years: 1979-2001

Fitment

• Johnson/Evinrude 3 cylinder outboards: 60, 65, 70, and 75 HP, 1979-2001

Replaces (OEM)

• 763777
• 584562
• 584269
• 583378
• 583131
• 581949
• 583060
• 582724

Frequently Asked Questions

What engines does the Sierra 18-99406 timer base fit? The Sierra 18-99406 fits Johnson and Evinrude 3 cylinder outboards rated at 60, 65, 70, and 75 HP built from 1979-2001.

Is the Sierra 18-99406 a direct OEM replacement? Yes, part number 18-99406 is designed as a direct replacement for the original factory timer base on the applicable Johnson/Evinrude 3 cylinder engines.

Which OEM part numbers does 18-99406 replace? It replaces OEM numbers 763777, 584562, 584269, 583378, 583131, 581949, 583060, and 582724.

Will this timer base work on a 2 cylinder or 4 cylinder Evinrude? No, the 18-99406 timer base is built for 3 cylinder Johnson/Evinrude engines only; it is not interchangeable with 2 or 4 cylinder timer base assemblies.

How much does the 18-99406 timer base weigh? The Sierra 18-99406 timer base weighs 0.9 pounds.

What are the dimensions of the 18-99406 timer base? The unit measures 8 x 5 x 3 inches.

What symptoms indicate a failed timer base on these outboards? Rough idle, misfiring, or hard starting on a 1979-2001 3 cylinder Johnson/Evinrude 60-75 HP outboard can point to a worn timer base like the 18-99406 replaces.

Does the 18-99406 include mounting hardware? The listing covers the timer base assembly itself, part number 18-99406; check your engine's original hardware for reuse during installation.

Can I use the 18-99406 on a 65 HP Johnson from the covered years? Yes, the 18-99406 is designed to fit 60, 65, 70, and 75 HP 3 cylinder Johnson/Evinrude engines within the 1979-2001 range.

Is professional installation required for the 18-99406 timer base? Installation involves ignition timing components, so buyers unfamiliar with outboard ignition systems on 3 cylinder Johnson/Evinrude engines should have the 18-99406 installed by a qualified marine technician.