Sierra 18-5139 Contact Set - Replaces Mercury/Mariner 336-4318A2 for Outboard Motors

The Sierra 18-5139 is a replacement ignition contact set (points) for Mercury/Mariner outboard motors. Contact sets are a core ignition tune-up component, opening and closing to time the spark at each cylinder; worn, pitted, or misaligned points cause hard starting, rough idle, misfires, and lost power, so replacing them on schedule during a tune-up keeps ignition timing accurate and the engine running smoothly. The set is built with an aluminum construction and finished in white.

This is packaged as a direct equivalent to the Mercury Marine OEM contact set: two units of the Sierra 18-5139 equal one OEM 336-4318A2 contact set, so order quantity accordingly to match the OEM package count. It is commonly installed alongside a matching condenser as part of a full ignition tune-up on Mercury/Mariner outboards. Every Sierra part carries Sierra's standard customer satisfaction warranty.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5139
• Product Type: Ignition Contact Set
• Compatible Application: Mercury/Mariner Outboard Motor
• Material: Aluminum
• Color: White
• Weight: 0.02 pounds
• UPC: 030999318367
• Packaging Note: 2 x Sierra 18-5139 = 1 x OEM 336-4318A2

Fitment

• Mercury/Mariner outboard motors

Replaces (OEM)

• 336-4318A2
• 336-4318A4
• 336-4318A3
• 336-3948A3
• 336-3948A2

Frequently Asked Questions

What does the Sierra 18-5139 contact set replace? The Sierra 18-5139 is a direct equivalent for Mercury Marine OEM contact sets 336-4318A2, 336-4318A4, 336-4318A3, 336-3948A3, and 336-3948A2.

How many contact sets come in a package of the 18-5139? Two units of the Sierra 18-5139 equal one OEM 336-4318A2 contact set, so check your engine's original packaging quantity when ordering.

What is a contact set used for on an outboard motor? A contact set, also called ignition points, opens and closes to time the spark delivered to each cylinder; it is a standard wear item replaced during an ignition tune-up on Mercury/Mariner outboard motors.

What engines does the 18-5139 contact set fit? This contact set is designed for Mercury/Mariner outboard motors that use the OEM 336-4318A2 series contact set.

What is the 18-5139 contact set made of? The Sierra 18-5139 has an aluminum construction and is finished in white.

How much does the 18-5139 contact set weigh? The Sierra 18-5139 contact set weighs 0.02 pounds.

Is the Sierra 18-5139 a genuine Sierra part or aftermarket equivalent? It is a Sierra-branded aftermarket replacement engineered to the same fit and function as the Mercury Marine OEM contact sets it replaces, and it is covered by Sierra's standard customer satisfaction warranty.

Do I need to replace the condenser at the same time as the 18-5139 contact set? Contact sets are commonly replaced together with a matching condenser as part of a full ignition tune-up, though the condenser is a separate Sierra part number from the 18-5139 contact set.

What is included when I order the 18-5139? Each order of Sierra 18-5139 includes the contact set only; remember that two units equal one OEM 336-4318A2 set, so verify quantity needed for your tune-up.

What are the signs a contact set needs replacing? Hard starting, rough idle, misfiring, and reduced power are common symptoms of worn or pitted contact points, and installing the Sierra 18-5139 restores accurate ignition timing.

Can I cross-reference the 18-5139 using an OEM Mercury part number? Yes, the Sierra 18-5139 cross-references to Mercury Marine 336-4318A2, 336-4318A4, 336-4318A3, 336-3948A3, and 336-3948A2.