Mercury – Quicksilver Spark Plug | Ignition System Component | NGK BU8H Semi-Surface Gap | 13686Q

Overview

A smooth, clean spark is the heartbeat of your engine, and the Mercury Marine 13686Q Quicksilver Spark Plug (NGK BU8H) keeps that heartbeat steady. Built with a semi-surface discharge design, it delivers efficient ignition and helps burn away carbon buildup before it can foul your plugs. Whether you’re easing out of the marina or opening up on the bay, this plug keeps your outboard firing crisp and clean. It’s dependable, tough, and designed specifically for marine use — the kind of plug you install and then forget about because it just works.

Key Features

• Purpose: Provides consistent, clean ignition and prevents fouling for smooth performance.
• Design: Features NGK’s semi-surface discharge style with small side electrodes — no gap adjustment needed.
• Material: Built with a pure alumina silicate ceramic insulator for strength, heat transfer, and break resistance.
• Core: Copper center electrode draws away heat for efficient combustion and reduced pre-ignition.
• Protection: Trivalent metal plating prevents corrosion and makes plug removal easier.
• Performance: Ribbed suppressor seal prevents “flash over” and misfire; triple seal design eliminates leakage.
• Ease of Use: Pre-gapped and ready to install using a standard spark plug socket.

Engine & Boat Compatibility

• Designed for select Mercury and Mariner TwoStroke outboards that specify NGK BU8H plugs in the owner’s manual.
• Commonly used in midrange outboards between 30 and 90 horsepower.
• Ideal for fishing boats, pontoons, inflatables, and utility craft powered by dependable Mercury TwoStroke engines.
• Always check your engine’s owner’s or service manual to confirm compatibility before installation.

Performance & Practical Benefits

The 13686Q spark plug is made for real-world boating. Its semi-surface design improves ignition even when carbon starts to build up — keeping your engine firing when cheaper plugs would foul. The copper core dissipates heat fast, preventing pre-ignition or knocking, while the ceramic insulator keeps the plug stable under high compression.

You’ll notice quicker starts, smoother idle, and more consistent throttle response across all RPMs. It also resists seizing in the cylinder head, so when it’s time to replace them, they back out easily without a fight. It’s a small piece of equipment that plays a big role in your engine’s reliability, efficiency, and performance.

Why Buy OEM

Not every spark plug is up to the job of marine duty. Automotive plugs can corrode, stick, or overheat when exposed to salt and moisture. The Quicksilver 13686Q — paired with NGK’s BU8H design — is tested and approved by Mercury Marine for the exact conditions your outboard faces.

It’s engineered to last longer, resist corrosion, and deliver steady spark energy in wet, hot, and high-vibration environments. With OEM-grade quality, you’re not just getting a plug — you’re getting a proven ignition component that keeps your Mercury engine performing the way it was designed to.

FAQ

Q1: Which engines use the 13686Q spark plug?
It fits select Mercury and Mariner TwoStroke outboards that specify NGK BU8H plugs — check your owner’s manual to confirm.

Q2: What makes this plug different from standard automotive plugs?
It’s built for marine use — corrosion resistant, self-cleaning, and designed to perform under heavy load and long idle times.

Q3: Does it require gapping before installation?
No. The semi-surface discharge design comes pre-gapped to factory specs.

Q4: How often should spark plugs be replaced?
It depends on your usage, but most boaters replace them once per season or after 100 hours of operation.

Q5: Can this be used in both saltwater and freshwater environments?
Yes — its corrosion-resistant plating is made for both.