Marine Parts Advisor: CDI Electronics Marine Ignition Systems

April 17, 2018

Our goal is to educate you about the purpose and function of many of the marine parts required to keep your boat running smoothly. Whether you're a veteran seaman or a novice, one thing you all know is that a boat comes equipped with hundreds of moving parts.

No one person can know everything there is to know about the proper functioning of every boat part. That's why we've tapped the collective wisdom of our long-time technical experts to share their knowledge and expertise.

What You Need to Know About Your Johnson Evinrude Power Pack & Mercury Switchbox

There’s not a lot of product care for an outboard ignition other than spark plug changes. It typically either works or it doesn’t, although on occasion you can experience an intermittent (ghost) problem. With typical outboard engines, replacement parts are represented by a few groups: the power pack (or switchbox), the stator, the outboard ignition trigger assembly, the ignition coils, the plug wires, and the spark plugs. Each component is necessary for ignition to occur.

Later design Electronic Fuel Injection (EFI) outboards have eliminated some of these ignition components.

As with any engine, battery condition, cables, and battery, the connections are critical and the key to ignition operation. Cables also need to be clean and in good condition; connections need to be tight.

Johnson & Evinrude and BRP refer to the ignition control module as a “power pack” and Mercury uses the term “switchbox.” Johnson & Evinrude like to refer to the ignition timing device as a "timer base" and Mercury uses the word "trigger." Both function for the same purpose which is to determine the correct time for a spark to occur.

Here’s the basic technical description:

Switchboxes, or power packs, are like the brain of the ignition system.
The stator, trigger, temperature switch, shift interrupt switch and kill switch provide inputs to the switchbox.
The switchbox has outputs to the ignition coil(s) and determines when it should fire the spark plug.

There are really no moving components to the ignition system other than the trigger and flywheel. The trigger rotates on the engine block below the flywheel to change ignition timing and the flywheel has magnets that provide an impulse to the stator.

Engine timing advance is controlled by the trigger movement. The switchbox fires the ignition coil which needs to happen at the correct time for optimal performance. There’s also a stator underneath the flywheel which provides the electrical input to the switch box.

Mercury Switchboxes
CDI-114-5772 Mercury switchbox
CDI-114-4953-32 Mercury switchbox
CDI-114-6222 Mercury switchbox
CDI-114-7509 Mercury/Force switchbox
CDI-114-7778 Mercury switchbox
CDI-114-7452K 1 Mercury switchbox
CDI-114-9052 Mercury/Mariner switchbox 3-cyl.
CDI-114-5713 Mercury/Mariner switchbox 2-cyl.

Trigger - Mercury
CDI-134-6452 - Mercury 4-cyl. Trigger

A Note About Johnson & Evinrude Optical Power Packs & Optical Sensor

An optical power pack describes the way the ignition system is triggered. An optical power pack uses a photocell. As the engine crankshaft rotates, a timing wheel passes an open or closed window by the stationary optical sensor that provides a signal to the power pack.

The signal to the power pack determines the direction of rotation, crankshaft piston position and when to provide a spark to a specific cylinder. The optical sensor rotates through linkage with the throttle position to provide ignition advance as RPMs increase.

Stators

A stator serves two functions and represents an integral part of the ignition system:

It charges the battery through the regulator/rectifier.
It provides the electrical current, e.g. voltage, to the ignition system.

Stators are OEM designed and specified to a single engine model or a family of engines. One thing that’s changed over the last 10-20 years is the physical and output size of stators. This is due to the increased electrical demands in boats today.

DC power demand is high, so the outboard manufacturers have increased the size of the stator to provide as much charging amperage to the battery as they can, given the space limitations under the flywheel.

Some Mercury outboards use a belt-driven alternator for charging rather than a charging stator under the flywheel. Because current demand is so high, they prefer to mount a belt-driven alternator to provide battery charging.

Rectifiers/Regulators

As stated above, rectifiers/regulators are used for battery charging and are part of the whole electrical ignition system.

A rectifier converts AC voltage to DC. Based on the AC input voltage and amperage, the amount of DC charge output will change. As an outboard speeds up in RPMs, the amount of current which the stator is capable of producing increases. Outboards that use a rectifier are typically smaller outboards and the amperage isn't regulated like on larger horsepower engines.

A voltage regulator not only acts as a rectifier to convert AC voltage from the stator to DC but also controls the amount of charge current into the battery. It regulates or manages the charging of the battery so there is no harm to the battery from overcharging. The regulator is a more sophisticated part than a rectifier.

CDI-193-6048 Johnson & Evinrude 35-amp Rectifier - Sierra & Johnson & Evinrude replacement
CDI-193-3689 Johnson & Evinrude 35-amp Rectifier - Johnson & Evinrude replacement (GR)

Ignition Coils

Ignition coils are unique to an engine family. Its function is to provide an electrical pulse to the spark plug that jumps the gap creating a spark. The switchbox provides the voltage and current to the coil along with the signal for the coil to fire.

There is no maintenance, other then spark plugs and spark plug wires with these components, but if there is no spark, make sure connections are good, tight, the wiring is intact, and nothing has been pinched, clipped or cut by mistake.

Timer Bases - Johnson & Evinrude

The timer base provides a signal to the switchbox telling it what the crankshaft and piston position is in and when to fire the ignition coil. The timer base rotates and timing of when the spark occurs changes depending on the RPMs of the engine. The trigger base part numbers vary depending on the make and family of engines. For example, with OMC you have the V4, V6, inline 2-cylinder and 3-cylinder engines. Knowing the correct year, the engine model, and the serial number is vital to ordering the correct part.

Related Products:
CDI-133-3533 Johnson & Evinrude Timer Base
CDI-133-3853 Johnson & Evinrude 6-cyl. Timer Base for engines with Quick Start

Marine Ignition System Diagnostics

Outboard ignition systems are a technical item, so the typical boat owner won’t necessarily have the knowledge about how the ignition system works. It can be difficult to diagnose exactly what’s failed in the ignition system and why spark doesn't occur.

Ignition component failure can be due to another part of the ignition system not functioning properly. You should be aware that replacement of a failed part with a new part can occur again due to another part not functioning correctly.

Proper diagnosis and troubleshooting are essential to determining a failed ignition component. In some cases, boat owners or dealers will order and replace all the ignition components to save time diagnosing an issue or intermittent problem. It's up to the individual what works best for them.

You can always call or contact our technical experts for a proper diagnosis.

CDI also has excellent diagnostics and technical troubleshooting guides on their website.

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