The SS-77 Rectifier is a German-made, heavy-duty 3-post rectifier from Buckshot Racing #77. It converts AC to DC on Mercury / Mariner 2-stroke outboards. It’s designed as a modern replacement for the classic square Mercury rectifier used on 2-stroke outboards like the 135, 150, 175, 200 HP V6, 225 ProMax running 16-amp electrics, 260 ROS, and 300 Drag motors.
On these outboard engines, the stator produces AC voltage under the flywheel. The rectifier’s job is to convert that AC into DC so the battery charges and your electrical system, tachometer, and ignition all stay happy. This style is a rectifier-only unit (no built-in regulator), just like the original 3-post Mercury OEM part, making it a true drop-in for 16-amp, unregulated charging systems.
How the SS-77 Fits Your Mercury Charging System
If you’re running a 9 or 16-amp Mercury or Mariner V6 system—including performance engines like a 225 ProMax with 16-amp electrics, XR2, XR4, 200 EFI, 260 ROS, or 300 Drag—the charging path looks like this:
The stator under the flywheel sends AC out on the two yellow leads.
Those yellow wires feed the 3-post rectifier.
The rectifier converts that AC to DC and sends it out the red output lead to charge the battery and feed the harness.
The tach signal is derived from this same stator/rectifier circuit, so when the rectifier fails, the tach is often one of the first things you notice.
Because everything runs through the rectifier, a weak or failing unit can show up as a charging problem, a tach issue, or even an ignition miss at high RPM.
Common Symptoms of a Bad Mercury Rectifier
A failing 3-post rectifier can cause a surprising range of problems:
The tachometer quits or becomes erratic.
The battery doesn’t charge and voltage never rises above resting level when you rev the motor.
You feel a high-speed miss or the engine cuts out under load as system voltage drops.
In severe cases, the engine may shut down completely or repeatedly blow fuses.
Many owners first notice “just” a tach problem, only to find out later the battery has been running off residual charge because the rectifier quit charging long ago.
Quick Check – How to Spot a Failing Rectifier
A simple visual check can tell you a lot. With the battery switched off, disconnect the two yellow stator leads and the red output wire from the rectifier. Look closely at the base and the potting compound around the stud area. If you see bubbling, burnt spots, cracked potting, or melted plastic, the rectifier has almost certainly overheated and failed internally.
For a more detailed diagnosis, you can use a multimeter. Measure battery voltage at idle and then at a fast idle: on a healthy system it should rise above static battery voltage as RPM comes up. You can also use the diode-test function on the meter to check each leg of the rectifier for open or shorted diodes, but the bubbling/burnt potting is often the quickest giveaway.
Why Upgrade to the Buckshot Racing SS-77?
The SS-77 was built specifically to solve the weak-link nature of older 3-post rectifiers on high-RPM Mercury 2-strokes:
It’s German-made for tight quality control and consistent performance.
The electronics are fully potted, protecting them from vibration, moisture, and salt.
It uses the same 3-post layout as the OEM Mercury rectifier—two AC inputs from the stator and one DC output—so it bolts in place of the stock unit on 16-amp systems.
Compatibility and Cross-Reference Part Numbers
The Buckshot Racing SS-77 3-post rectifier is intended for Mercury / Mariner 2-stroke outboards using the classic square rectifier on 16-amp charging systems, including many 135–200 HP V6 models and performance V6 engines using 16-amp electrics.
It replaces a wide range of Merc OEM and aftermarket numbers, including: 154-6770, 18-5707, 49184, 62351A1, 62351A2, 70350A1, 70350A3, 72310, 8M0058226, 816770, 816770T, 9-17100
Includes one (1) brand-new SS-77 Mercury Rectifier
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.