Sierra Switch Box 18-99305 for Mercury Mercruiser 4-Cylinder 120hp Sport Jet 1995-1996 - Replaces 826866A2

The Sierra 18-99305 switch box is an ignition switch box built for 4-cylinder Mercury Mercruiser engines, specifically the 120hp Sport Jet model produced in 1995-1996. The switch box is a core component of the engine's ignition system, controlling spark timing and delivery to keep the engine firing correctly. Replacing a worn or failing switch box restores reliable starting and smooth running on engines where the original unit has degraded from age, vibration, or moisture exposure in the marine environment.

This switch box is a direct replacement for the OEM Mercury Mercruiser part 826866A2, so it installs in place of the original unit without modification to the ignition wiring or mounting points. It is intended for the 4-cylinder 120hp Sport Jet engine platform covered by that OEM number, making it a straightforward swap for owners maintaining or restoring this specific engine.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99305
• Product Type: Ignition Switch Box
• Engine Application: Mercury Mercruiser 4-Cylinder 120hp Sport Jet
• Model Years: 1995-1996
• Replaces (OEM): 826866A2
• Weight: 1 pound
• UPC: 808282396091

Fitment

• Mercury Mercruiser 4-Cylinder 120hp Sport Jet, 1995-1996

Replaces (OEM)

• 826866A2

Frequently Asked Questions

What does the Sierra 18-99305 switch box fit? The Sierra 18-99305 is built for the Mercury Mercruiser 4-cylinder 120hp Sport Jet engine from 1995-1996.

Is the 18-99305 switch box a direct replacement for the factory unit? Yes, the 18-99305 replaces OEM Mercury Mercruiser part number 826866A2 and installs in the same location without modifying the existing ignition wiring.

What OEM part number does the Sierra 18-99305 cross-reference? It replaces Mercury Mercruiser OEM number 826866A2.

How much does the switch box weigh? The Sierra 18-99305 switch box weighs 1 pound.

What engine ignition system is this switch box part of? The 18-99305 is an ignition switch box that controls spark timing and delivery for the Mercury Mercruiser 4-cylinder 120hp Sport Jet engine.

Will this switch box work on other Mercury Mercruiser engines besides the 120hp Sport Jet? The Sierra 18-99305 is specified for the 4-cylinder 120hp Sport Jet engine, 1995-1996; fitment outside that application is not confirmed.

What symptoms indicate the switch box needs to be replaced? Hard starting, misfiring, or a complete loss of spark on the 120hp Sport Jet engine are common signs the original switch box, replaced by the Sierra 18-99305, has failed.

Does installing the 18-99305 require rewiring the boat's ignition harness? No, the Sierra 18-99305 is a direct-fit replacement for OEM 826866A2 and uses the existing ignition wiring.

Is the Sierra 18-99305 a genuine OEM part or an aftermarket equivalent? The 18-99305 is a Sierra-branded replacement part manufactured to replace OEM Mercury Mercruiser part 826866A2, not a Mercury-branded original part.

What is the part number printed on this switch box? The part is identified by Sierra part number 18-99305.