The Buckshot Racing #77 Wizard Switchbox-to-Coil Wire Harness Set is a premium replacement for the primary ignition leads used between the dual switchboxes and six ignition coils on compatible Mercury and Mariner V6 two-stroke outboards.
On these engines, each switchbox sends the primary ignition pulse to three coils. Mercury parts catalogs list one harness for cylinders 2-4-6 and another for 1-3-5, so the complete set serves all six cylinders.
Mercury currently lists later versions such as 84-69738A9 and 84-69739A6 on some V6 applications, while earlier racing and production engines commonly used 84-69738A7 and 84-69739A2.
For high-RPM Mercury performance engines, these short primary leads are an important part of the ignition system. They do not set ignition timing by themselves, but they carry the switchbox output to the coils. Corroded terminals, brittle insulation, loose crimps, or damaged conductors can cause intermittent spark, misfire, and inconsistent ignition performance.
Built for Outboard Boat Racing and High Performance Use
Wizard harnesses use 14 AWG tinned stranded copper conductors for strong current capacity and improved corrosion resistance in the marine environment. The conductors are covered with high-temperature red fiberglass insulation, while the terminals are mechanically crimped, soldered, and protected with black rubber boots.
Each lead is color-coded and numbered to simplify installation and reduce the chance of connecting a coil to the wrong switchbox output.
The complete kit includes both the port and starboard three-wire harnesses, providing all six primary coil leads needed for a V6 dual-switchbox ignition system.
Mercury 2.0, 2.4, 2.5 Liter V6 Fitment
These harnesses are intended for Mercury and Mariner V6 engines using the 69738 / 69739-style switchbox-to-coil harness arrangement.
Verified Mercury parts listings show this harness family on V6 engines including the V-150, older 150 XR-2 / Magnum / Marathon V6, and Mercury Racing 2.5L EFI applications. Mercury Racing diagrams specifically show 69738A7 for cylinders 2-4-6 and 69739A2 for cylinders 1-3-5 on compatible 2.5L EFI engines.
The same basic six-wire replacement arrangement is cataloged by CDI Electronics as 934-9738, designed for Mercury and Mariner V6 engines and cross-referenced to 84-69738, 84-69738A1, 84-69738A7, 84-69739, 84-69739A1 and 84-69739A2. CDI describes the set as six wires: two green, two green/white, and two green/red.
Common compatible engine families include many 2.0L, 2.4L and 2.5L V6 two-strokes using the traditional dual-switchbox ADI ignition, including selected 135, 150, 175 and 200 HP, XR2, XR4, XR6, Laser EFI, XRi, Pro Max, and compatible Mercury Racing engines such as 2.4L Bridgeport, 245 Carb, 260 EFI, S3000 and 300 Drag-style applications where the original ignition system uses this harness architecture.
Because Mercury used several ignition layouts over the years, fitment should be confirmed by the existing harness number and ignition configuration, not horsepower alone.
Replaces Mercury & Aftermarket Harness Numbers
The Wizard set is designed as an upgraded replacement for the common Mercury switchbox-to-coil harness family, including: 84-69738, 84-69738A1, 84-69738A7, 84-69739, 84-69739A1, 84-69739A2, CDI Electronics 934-9738
Later Mercury service replacements may use suffixes such as 69738A9 and 69739A6, so always compare the existing harness and engine parts diagram before ordering.
Why Replace Old Coil Primary Harnesses?
These wires live in a high-heat, high-vibration environment directly under the cowl. After years of service, original insulation can harden, terminals can corrode, and crimp connections can loosen internally.
That can create intermittent ignition problems that are difficult to diagnose, especially at high RPM where vibration and electrical demand are greatest.
Replacing aged primary harnesses is especially worthwhile during a switchbox replacement, coil service, complete ignition refresh, or race-engine rebuild, because it removes another potential failure point between the switchboxes and coils.
Buckshot Racing #77 Tech Tip
Before installation, confirm the engine uses the dual-switchbox V6 ignition system and identify which harness feeds cylinders 1-3-5 and which feeds 2-4-6.
Route the new leads the same way as the original harnesses, keep them clear of flywheel contact and sharp edges, and make sure every terminal is fully seated and protected by its boot.
If an engine has a persistent no-spark or three-cylinder ignition problem, do not assume the harness is the only cause. The stator, trigger, switchboxes, grounds, stop circuit, and coils should still be tested using the proper DVA and service-manual procedures.
The Buckshot Racing #77 Wizard Switchbox-to-Coil Wire Harness Set provides a clean, heavy-duty replacement for one of the most overlooked parts of the classic Mercury V6 ignition system, making it a strong upgrade for both restoration and high-performance applications.
Contact Mike Hill at mike@buckshotracing77.com or 714-697-1716 with any questions.