Sierra 18-5777-1 Switch Box, Replaces Mercury 339-7452A19, Fits Mercury 15/20 HP Outboards

The Sierra 18-5777-1 Switch Box is an ignition switch box built to meet or exceed the quality of the original equipment part it replaces. It is designed for Mercury outboard engines in the 15 HP and 20 HP range across specific serial number breaks, controlling the ignition timing and spark delivery that keeps the engine firing correctly. The housing has a machined exterior finish and is finished in black to match factory Mercury components.

Because ignition switch boxes are serial-number and horsepower specific on Mercury outboards, buyers should confirm the HP rating and serial number range of their engine against the fitment listed below before ordering. The 18-5777-1 is cross-referenced to several OEM and aftermarket part numbers, making it a direct swap for engines currently fitted with any of those original components. It ships as a single switch box unit ready to install in place of the worn or failed original.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5777-1
• Color: Black
• Product Dimensions: 2.62 x 6 x 11.25 inches
• Weight: 0.66 pounds
• Exterior Finish: Machined
• UPC: 808282392628
• Fitment: Mercury outboard, 15 HP and 20 HP
• OEM Cross Reference: CDI 114-7452K1, Mallory 9-25102, Mercury 339-7452A19, 339-7452A15, 339-7452A7, 339-7452A9

Fitment

• Mercury 15 HP, serial number B292414 through G760299
• Mercury 15 HP, serial number G760300 and up
• Mercury 15 HP, serial number G438000 through G760299
• Mercury 20 HP, serial number 6443973 through G044026
• Mercury 20 HP, serial number G438000 through G760299

Replaces (OEM)

• CDI 114-7452K1
• Mallory 9-25102
• Mercury 339-7452A19
• Mercury 339-7452A15
• Mercury 339-7452A7
• Mercury 339-7452A9

Frequently Asked Questions

What engines does the Sierra 18-5777-1 switch box fit? The 18-5777-1 fits Mercury outboard engines rated 15 HP and 20 HP within specific serial number ranges, including 15 HP units from serial B292414 through G760299, 15 HP units from G760300 and up, 15 HP units from G438000 through G760299, 20 HP units from 6443973 through G044026, and 20 HP units from G438000 through G760299.

Is the 18-5777-1 switch box interchangeable with OEM Mercury parts? Yes, the Sierra 18-5777-1 cross-references directly to Mercury 339-7452A19, 339-7452A15, 339-7452A7, and 339-7452A9, so it is a direct swap for engines currently fitted with any of those Mercury part numbers.

Does the 18-5777-1 replace any CDI or Mallory switch boxes? Yes, the Sierra 18-5777-1 also cross-references to CDI 114-7452K1 and Mallory 9-25102, making it a direct replacement for those aftermarket ignition switch boxes as well.

How much does the Sierra 18-5777-1 switch box weigh? This switch box weighs 0.66 pounds.

What are the dimensions of the 18-5777-1 switch box? The switch box measures 2.62 x 6 x 11.25 inches.

What color is the Sierra 18-5777-1 switch box? It is finished in black with a machined exterior.

Is the 18-5777-1 a genuine Sierra part or an aftermarket copy? The 18-5777-1 is a genuine Sierra switch box, built to meet or exceed the quality of the original Mercury equipment part it replaces rather than being a generic aftermarket copy.

What is included when I order the 18-5777-1 switch box? Ordering the Sierra 18-5777-1 includes one complete ignition switch box unit, ready to install in place of the original equipment switch box.

How do I confirm the 18-5777-1 is the correct switch box for my Mercury outboard? Check your Mercury outboard's horsepower rating and engine serial number against the fitment ranges for the 18-5777-1: 15 HP or 20 HP engines within the serial breaks listed for this part, since ignition switch boxes on these engines are serial-number specific.

What does the switch box do on a Mercury outboard? On the Mercury 15 HP and 20 HP outboards this part fits, the switch box manages ignition timing and spark delivery, and the Sierra 18-5777-1 is designed to perform this function as a direct replacement for the original unit.