Sierra Switch Box 18-5776-1 for Mercury 18 HP and 25 HP Outboard Motors

The Sierra 18-5776-1 Switch Box is an ignition switch box built to meet or exceed the quality of the original equipment part it replaces. It serves as the ignition control component on select Mercury outboard motors, managing the electrical signal that fires the spark at the correct time for reliable engine starting and running performance. The switch box is a direct fit for the specific Mercury outboard applications listed below, so confirming your engine's serial number before ordering is important to ensure proper fit.

This switch box is engineered as a precise replacement, matching the form, fit, and function of the original Mercury switch box on covered applications. It is compatible with aftermarket cross-reference parts from other major ignition brands, giving boat owners a dependable option when sourcing a replacement for aging or failed ignition components.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5776-1
• Category: Mercury Outboard Switch Box
• Weight: 0.21 pounds
• Color: White
• Mounting Type: Engine
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• UPC: 808282392611

Fitment

• Mercury 18 HP outboard, serial numbers 5837437 to 6443972
• Mercury 25 HP outboard, serial numbers 5705532 to 6443972
• Mercury 25 HP outboard with nut connection, serial numbers 6443973 and up

Replaces (OEM)

• CDI 114-7452A3
• Mallory 9-25101
• Mercury 339-7452A3
• Mercury 339-7452A2
• Mercury 339-7452A1
• Mercury 899883230

Frequently Asked Questions

What is the Sierra 18-5776-1 switch box used for? The Sierra 18-5776-1 is an ignition switch box that controls the timing of the spark signal on compatible Mercury outboard motors, and it is required for the engine to start and run.

Which Mercury outboards fit the 18-5776-1 switch box? This switch box fits Mercury 18 HP outboards with serial numbers 5837437 to 6443972, and Mercury 25 HP outboards with serial numbers 5705532 to 6443972 or, for the nut connection version, serial numbers 6443973 and up.

How do I know if my engine uses the nut connection version? Mercury 25 HP outboards with serial number 6443973 and up use the nut connection switch box, which is the configuration supplied by the Sierra 18-5776-1; earlier 25 HP serial numbers in the 5705532 to 6443972 range use a different connection type.

What OEM part numbers does the 18-5776-1 switch box replace? The Sierra 18-5776-1 cross-references to Mercury 339-7452A3, 339-7452A2, 339-7452A1, and 899883230, as well as CDI 114-7452A3 and Mallory 9-25101.

Is the Sierra 18-5776-1 an OEM or aftermarket switch box? It is an aftermarket switch box manufactured by Sierra that is designed to meet or exceed the quality of the original Mercury equipment it replaces.

What color is the 18-5776-1 switch box? The switch box has a white finish.

How much does the Sierra 18-5776-1 switch box weigh? The Sierra 18-5776-1 switch box weighs 0.21 pounds.

What are the dimensions of the 18-5776-1 switch box? The unit measures 0.39 x 0.39 x 0.39 inches.

Can I use the 18-5776-1 on any Mercury outboard? No, fit is specific to certain Mercury 18 HP and 25 HP outboards by serial number range, so the serial number should be checked against the fitment before ordering the 18-5776-1.

Does the switch box come as a single unit? Yes, the Sierra 18-5776-1 is supplied as one switch box unit.

Is there a different part number for other Mercury serial ranges? Yes, other Mercury 18, 20, and 25 HP serial ranges use a different Sierra switch box part number, so confirming the exact serial number is necessary before ordering the 18-5776-1.