Sierra 18-99229 Mercury Mariner Switch Box - 6 Cylinder - Replaces 18495A31, 18495A32, 18495A22, 18495A23 - Fits 175 & 210 HP (1997-2005)

The Sierra 18-99229 is a Mercury/Mariner ignition switch box built for 6-cylinder outboard engines. It serves as the ignition switching component in the engine's ignition circuit, directing spark timing signals to keep the engine firing correctly. This switch box is designed as a direct replacement for the factory Mercury/Mariner switch box on 175 and 210 HP six-cylinder outboards from the 1997-2005 model years, making it a straightforward swap for boat owners dealing with hard starting, misfiring, or a no-spark condition traced back to a failed switch box.

As an ignition system component, the switch box works alongside the coils, trigger, and stator to manage spark delivery across all six cylinders. Replacing a worn or failed switch box with the Sierra 18-99229 restores reliable ignition timing without the cost of a full ignition system overhaul. The part is identified by the Sierra part number 18-99229 and is cataloged specifically for the 6-cylinder Mercury/Mariner application described below.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99229
• Application: Mercury Mariner Switch Box, 6 Cylinder
• Cylinder Count: 6 Cylinder
• Weight: 0.9 pounds
• Product Dimensions: 7 x 4 x 2 inches
• UPC: 808282393960

Fitment

• Mercury/Mariner 6-cylinder outboard engines, 175 and 210 HP, 1997-2005

Replaces (OEM)

• 18495A31
• 18495A32
• 18495A22
• 18495A23

Frequently Asked Questions

What engines does the Sierra 18-99229 switch box fit? The Sierra 18-99229 fits Mercury and Mariner 6-cylinder outboard engines rated at 175 and 210 HP, for the 1997-2005 model years.

What OEM part numbers does the 18-99229 switch box replace? It replaces OEM Mercury/Mariner numbers 18495A31, 18495A32, 18495A22, and 18495A23.

How much does the Sierra 18-99229 switch box weigh? It weighs 0.9 pounds.

What are the dimensions of this switch box? The switch box measures 7 x 4 x 2 inches.

Is the Sierra 18-99229 a direct replacement for my factory switch box? Yes, the 18-99229 is built to replace the factory Mercury/Mariner switch box on the 6-cylinder 175 and 210 HP applications listed for this part, using the same OEM cross-reference numbers.

What symptoms indicate my switch box needs replacing? Hard starting, engine misfire, or a no-spark condition on a Mercury/Mariner 6-cylinder outboard often point to a failed switch box like the one the Sierra 18-99229 replaces.

Does the switch box come with mounting hardware? The Sierra 18-99229 is supplied as the switch box unit itself; check your engine's factory hardware for reuse during installation.

Will the 18-99229 work on a 4-cylinder Mercury outboard? No, the 18-99229 is cataloged specifically for 6-cylinder Mercury/Mariner outboards, not 4-cylinder engines.

Is this switch box compatible with both Mercury and Mariner branded outboards? Yes, the Sierra 18-99229 is designed for both Mercury and Mariner 6-cylinder outboards in the 175 and 210 HP range.

What is the Sierra part number for this switch box? The part number is 18-99229.

Can I confirm fitment by cross-referencing my old part number? Yes, if your old switch box is marked 18495A31, 18495A32, 18495A22, or 18495A23, the Sierra 18-99229 is the replacement for it.