Sierra 18-5790-1 Switch Box for Mercury Sport Jet 120 HP, Replaces 18495A12

The Sierra 18-5790-1 Switch Box is a replacement ignition switch box built for Mercury Sport Jet 120 HP outboards, serial number E138600 and up. The switch box is the component in the ignition system that fires the spark plugs in the correct sequence, and a worn or failing unit is a common cause of hard starting, misfiring, or a no-spark condition. This Sierra unit is manufactured to meet or exceed the performance of the original equipment part it replaces, giving boat owners a reliable option when the factory switch box needs to be swapped out.

The 18-5790-1 cross-references directly to several OEM and aftermarket switch box numbers, including Mercury, Mercury Sport Jet, Chrysler, CDI, and Mallory part numbers, so it can be matched against whichever number is stamped on the failed unit or listed in the engine's parts manual. It ships as a single switch box unit with a white housing and is sized for direct mounting in place of the original component.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5790-1
• Product Category: Mercury Outboard Switch Box
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Color: White
• Weight: 0.79 pounds
• UPC: 808282392512

Fitment

• Mercury Sport Jet, 120 HP, model years 1996-99, serial number E138600 and up

Replaces (OEM)

• CDI 114-4953
• Chrysler 18495A12
• Mallory 9-25107
• Mercury 18495A26
• Mercury 18495A19
• Mercury Sport Jet 18495A12

Frequently Asked Questions

What does the Sierra 18-5790-1 switch box fit? The Sierra 18-5790-1 is built for Mercury Sport Jet 120 HP outboards with serial number E138600 and up, covering model years 1996-99.

Is the 18-5790-1 an OEM Mercury part or an aftermarket replacement? It is a Sierra-manufactured aftermarket switch box designed to meet or exceed the performance of the original equipment switch box it replaces, including Mercury 18495A26 and 18495A19.

Which OEM part numbers does this switch box cross-reference? The 18-5790-1 cross-references to Mercury 18495A26, Mercury 18495A19, Mercury Sport Jet 18495A12, Chrysler 18495A12, CDI 114-4953, and Mallory 9-25107.

How much does the switch box weigh? The Sierra 18-5790-1 switch box weighs 0.79 pounds.

What color is the housing? The switch box housing is white.

What are the dimensions of the switch box? The 18-5790-1 measures 0.39 x 0.39 x 0.39 inches.

What symptoms indicate my Sport Jet switch box needs replacement? Hard starting, engine misfire, or a no-spark condition on a Mercury Sport Jet 120 HP outboard are common signs the switch box, such as the Sierra 18-5790-1, has failed and needs replacement.

What is included when I order this part? Ordering this listing includes one Sierra 18-5790-1 switch box unit.

Will this switch box work on Mercury Sport Jet 90 models? No, the 18-5790-1 is specified for Mercury Sport Jet 120 HP outboards with serial number E138600 and up; earlier 90 HP and lower-serial 120 HP Sport Jet engines use different Sierra switch box part numbers.

Can I use the serial number to confirm this is the correct switch box? Yes, the Sierra 18-5790-1 is specified for Mercury Sport Jet 120 HP engines with serial number E138600 and up, so checking your engine's serial number against that range confirms fitment.