Sierra Regulator/Rectifier 18-99394, 35-Amp, for Johnson Evinrude Outboards

The Sierra 18-99394 is a 35-amp regulator/rectifier built for Johnson and Evinrude outboard charging systems. It converts the raw AC output from the outboard's stator into regulated DC current, protecting the battery and onboard electronics from overcharging while keeping the charging voltage within a safe, consistent range. As the charging system ages, a failing regulator/rectifier is one of the most common causes of a battery that will not hold a charge, erratic voltage readings, or a battery that overcharges and boils dry, and replacing this component restores proper charging output.

This unit is designed as a direct-fit replacement for the applicable Johnson Evinrude outboard charging system, mounting in place of the factory regulator/rectifier using the existing mounting points and wiring. It is a straightforward maintenance-level replacement for anyone servicing an aging or underperforming charging circuit on a Johnson or Evinrude outboard.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99394
• Category: Evinrude Outboard Rectifier Regulator
• Amperage: 35 amps
• Output Type: Regulator/Rectifier (AC to regulated DC)
• Weight: 1 pound
• UPC: 808282394271

Fitment

Fits Johnson and Evinrude outboard engines.

Frequently Asked Questions

What does the Sierra 18-99394 regulator/rectifier do? It converts the AC current produced by a Johnson or Evinrude outboard's stator into regulated DC current, controlling charging voltage so the battery charges properly without being overcharged.

What engines does the 18-99394 fit? The Sierra 18-99394 is designed for Johnson and Evinrude outboard engines equipped with a 35-amp charging system.

How many amps does this regulator/rectifier handle? It is rated for 35 amps of charging output.

How much does the 18-99394 weigh? The Sierra 18-99394 regulator/rectifier weighs 1 pound.

What are the symptoms of a failing regulator/rectifier? A weak or dying battery, overcharging that boils battery fluid, erratic voltage readings, or a battery that will not hold a charge are common signs the regulator/rectifier on a Johnson or Evinrude outboard needs replacement.

Is the 18-99394 a direct replacement for the factory unit? Yes, the Sierra 18-99394 is designed to mount in place of the original Johnson Evinrude regulator/rectifier using the existing mounting points and wiring.

Can I install this regulator/rectifier myself? Installation is a standard maintenance-level task involving disconnecting the old unit's wiring, mounting the Sierra 18-99394 in the same location, and reconnecting the charging circuit wiring.

Does the 18-99394 include mounting hardware? The dossier for the Sierra 18-99394 does not specify included mounting hardware; confirm hardware needs against your existing charging system components before installing.

What is the difference between a regulator and a rectifier? The Sierra 18-99394 combines both functions in one unit: the rectifier converts AC output from the stator into DC, and the regulator controls that DC output to a safe, consistent voltage for charging the battery.

Is the Sierra 18-99394 a genuine Sierra part? Yes, 18-99394 is the Sierra manufacturer part number for this Johnson Evinrude regulator/rectifier.