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 t