Sierra Mercury Mariner 40 Amp Voltage Regulator 18-99442, Replaces 18736

The Sierra 18-99442 is a 40 amp voltage regulator built for Mercury and Mariner outboard engines. It manages charging output from the outboard's alternator/stator system, regulating voltage delivered to the battery so onboard electronics and the starting battery receive a steady, controlled charge. A failed or failing regulator is a common cause of overcharging, undercharging, or a battery that will not hold a charge on Mercury and Mariner outboard applications, and replacing it with a properly rated 40 amp unit like the 18-99442 restores correct charging system operation.

This regulator is a direct cross-reference for OEM number 18736, making it a straightforward swap for boat owners and marine technicians servicing the charging system on Mercury/Mariner outboards. It is sold as a standalone replacement part, so no separate wiring harness or bracket is included unless otherwise noted.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99442
• Amp Rating: 40 Amp
• Application: Mercury/Mariner Outboard
• Weight: 1.6 pounds
• UPC: 808282396268

Fitment

Mercury/Mariner outboard engines.

Replaces (OEM)

• 18736

Frequently Asked Questions

What does the Sierra 18-99442 voltage regulator do? The Sierra 18-99442 regulates the charging voltage produced by a Mercury/Mariner outboard's alternator, controlling how much current flows to the battery so it charges correctly without overcharging or undercharging.

Is the Sierra 18-99442 a 40 amp or a lower-amperage regulator? It is a 40 amp voltage regulator, matching the charging output of the Mercury/Mariner outboard systems it is designed to service.

Does 18-99442 replace OEM part 18736? Yes, Sierra part 18-99442 is a direct cross-reference for OEM number 18736.

What engines does the 18-99442 regulator fit? This regulator is built for Mercury and Mariner outboard engines.

How much does the 18-99442 regulator weigh? The Sierra 18-99442 weighs 1.6 pounds.

Is this regulator new or remanufactured? The Sierra 18-99442 is a new replacement voltage regulator, not a remanufactured or repaired unit.

What is the UPC for the Sierra 18-99442 regulator? The UPC for the Sierra 18-99442 Mercury/Mariner voltage regulator is 808282396268.

Why would I need to replace the voltage regulator on my Mercury outboard? A worn or failed voltage regulator like the one replaced by the 18-99442 commonly causes overcharging, undercharging, or a battery that will not hold a charge, so replacing it restores correct charging system function.

Does the 18-99442 include mounting hardware or a wiring harness? The Sierra 18-99442 is sold as the regulator unit itself; no separate wiring harness or bracket is specified with this part.

Can I use part number 18736 to search for this regulator? Yes, 18736 is the OEM number that the Sierra 18-99442 directly replaces, so it can be used to cross-reference the correct part.