The Mercury Genuine OEM 8-pin key-switch wiring harness kits provide a factory-correct electrical connection between a compatible Mercury outboard or jet-drive powerhead and the boat’s helm.
Available as Mercury 816626A15 (15-Foot), 816626A20 (20-Foot) and 816626A25 (25-Foot), these engine-to-helm harness assemblies are designed for boats using Mercury’s conventional round 8-pin engine connector.
Each assembly combines the main boat-side wiring harness with an OEM ignition and choke key switch, audio warning horn and factory electrical connections for power trim, instrumentation and a lanyard stop switch.
The dash-mounted key switch installs in an approximately 2-1/8-inch mounting hole, providing a clean installation without assembling a key-switch harness from separate components.
The 84-816626A15, 84-816626A20 and 84-816626A25 Mercury boat-side engine harnesses use factory-style connectors, wire colors and circuit routing.
This preserves the engine’s ignition, starter, choke or fuel-enrichment, warning-horn, tachometer, trim and shutdown functions while reducing the need for splices or improvised connections.
Broad Mercury and Mariner Engine Compatibility
Mercury lists these harness assemblies for many Mercury and Mariner two-cycle outboards rated 6 HP to 300 HP that were manufactured in the United States or Belgium. Additional applications include oil-injected Japanese-built Mariner 30 and 40 HP two-strokes, USA-built Mercury and Mariner FourStroke outboards, Force 40 HP and larger engines from 1993 forward, and Mercury Jet Drive applications.
Fitment is determined by the engine’s connector and electrical system rather than horsepower alone.
These Mercury 8-pin key-switch harnesses are commonly associated with recreational and high-performance engine families ranging from smaller inline outboards through Mercury V6 models.
Mercury catalog usage includes 2.0 Liters, 2.4 Liters, 3.0 Liters, 2.5L EFI and 2.5L EFI Offshore, XR2, XR4, XR6, 150, 200, 225 EFI Pro Max/Super Magnum, 225X EFI Pro Max, 200XS 2.5L DFI, SportJet 90, 95XR, 120, 120XR and 120XR2, 175XR2 Jet Drive, 200 DFI Jet Drive and 250 DFI/M2 Jet Drive applications.
Because Mercury used different electrical configurations after 2012 with some horsepower and model families, the engine connector and serial number should always be checked before ordering.
Option One: Mercury 816626A15 — 15-Foot Harness
The Mercury 84-816626A15 key-switch harness provides a 15-foot, or approximately 4.57-meter, engine-to-helm cable. It is generally the best choice for smaller boats, compact fishing boats, runabouts, tunnel hulls and performance boats with the dashboard or control panel positioned relatively close to the transom.
The 816626A15 includes the integrated audio warning horn and electrical provisions for power trim, instrumentation and the lanyard stop circuit. It is also a replacement or superseding service assembly for several earlier Mercury key-switch harness numbers, including 90315A15, 13585A15, 14885A15 and 17925A15.
Option Two: Mercury 816626A20 — 20-Foot Harness
The Mercury 84-816626A20 key-switch harness uses the same factory 8-pin engine-to-helm configuration with a 20-foot, or approximately 6.1-meter, cable. The additional length is useful for bass boats, ski boats, center consoles and recreational performance boats where the harness must follow a longer protected route beneath the deck or along the gunwale.
The 816626A20 is supplied with the OEM key switch and audio warning horn, providing a complete control-side harness for compatible Mercury, Mariner, Force and Mercury Jet Drive systems.
Option Three: Mercury 816626A25 — Dual 25-Foot Harness Package
The Mercury 84-816626A25 harness assembly is intended for applications requiring the longest engine-to-helm routing. Mercury identifies this kit as a package containing two 25-foot, or approximately 7.6-meter, harnesses with matched ignition keys, making it especially useful for factory-style dual-engine installations.
Each 816626A25 harness includes an audio warning horn and connections for power trim, instrumentation and the lanyard stop switch.
Selecting the Correct Harness Length
Measure the complete intended routing path from the engine connector to the dashboard before selecting a harness. Follow the actual path around rigging tubes, bulkheads, steering components and under-deck supports rather than measuring in a straight line.
Allow sufficient additional length for service loops at the engine and behind the dashboard, but avoid excessive cable that must be tightly coiled or placed near moving steering components.
Choose the Mercury 816626A15 for a 15-foot harness, the 816626A20 for a 20-foot harness, or the 816626A25 for a 25-foot harness. These measurements refer to the actual harness length, not the length of the boat.
To determine the correct size, measure the complete routing path from the helm down to the gunwale, across the boat, through the rigging route, and out to the engine. Add approximately 2 feet to the measured distance to allow for bends, routing clearance, and service loops at the helm and motor.
The result is a clean, factory OEM harnessharness for restoring, rerigging or repowering a compatible Mercury-powered boat.
Contact Mike Hill at mike@buckshotracing77.com w/ technical questions