Mercury – Ignition Coil, 75–115HP 3-Cylinder & Various V6 | Ignition | 8M0077471

Overview

If you’ve run two-stroke Mercs for any length of time, you know how one weak ignition coil can make a good motor run like it woke up on the wrong side of the dock. A cylinder drops out, the idle gets lumpy, or the engine falls flat the moment you try to get the boat moving. This coil is the proper replacement for the 75–115HP 3-cylinder OptiMax motors, a bunch of Mercury and Mariner V6 two-strokes, and even the MerCruiser 600Sci. It’s built to hold spark in the hot, damp, vibrating mess that is a real marine engine compartment.

Key Features

 • Fits 75–115HP 3-Cyl OptiMax – Plus several V6 two-stroke Mercury and Mariner models.
 • Strong, Consistent Spark – Helps clear up misfires and hesitation.
 • Marine-Ready Build – Handles heat, moisture, and constant shaking without giving up early.
 • OEM-Grade Windings – Reduces random spark dropouts and cross-fire issues.
 • Bolts On Cleanly – No weird wiring tricks or adapters needed.

Engine & Boat Compatibility

 • 75–115HP Mercury OptiMax (3-cyl)
 • Mercury/Mariner V6 2-stroke outboards (various models)
 • MerCruiser 600Sci
 • EFI and OptiMax ignition systems

Performance & Practical Benefits

A fresh coil can make the motor feel a whole lot more settled. Idle cleans up, throttle response gets sharper, and the engine doesn’t lose a cylinder the moment you ask for some power. These engines rely on a crisp, steady spark—when one coil gets weak, the whole motor acts tired. Swapping in a good OEM coil usually brings that snap and confidence back.

Why Buy OEM

Marine ignition parts deal with more heat and moisture than automotive coils ever see. OEM coils last longer, fit right, and don’t cause the strange intermittent misses that cheaper coils are known for. You install it once, and it just works.

FAQ

Q1: How do I know the coil’s going bad?
A: A miss at idle, rough running, hard starts, or the engine falling flat under load.

Q2: Should I replace just one or do a set?
A: If the others are the same age, replacing them together saves you from another failure soon after.

Q3: Is this a tough install?
A: Not really—just match the wiring and bolt it down. Basic tools only.

Q4: Will this help with sluggish acceleration?
A: Yes. Weak coils often show up most when the engine is working hardest.

Q5: Saltwater ok?
A: Yep—this coil is built for the damp, hot, always-moving marine environment.

• Supersessions
  300-8M0077471, 300-8M0077471, 339-879984A1, 339-879984T00