Ignition System Tips

Ever have a problem starting a motor? Or did you ever have a motor start to miss, bog-down or otherwise just plain act up? Well, I don't know about you, but I've seen plenty over my life. And there is nothing more frustrating than have a motor act up when you want to enjoy it.

Although the best way to avoid this is a regimented maintenance program, the next best solution is being able to figure out why it happened, once it does.

And even if you've never turned a wrench before, it is a good idea to be at least passingly familiar with how to go about troubleshooting an engine problem in case it happens on the water.

The first thing I always tell neophytes when they want to understand their motor is the basics of how the motor works. Drawn out explanations of the Otto cycle engine aside, it all comes down to three things. In order for a motor to run you need compression, fuel and spark.

Compression indicates a mechanically sound motor, one that is capable of ingesting air/fuel and squeezing it so that the maximum benefit of the explosion which occurs in the cylinder(s) will produce the desired affect (of turning the propeller and moving the boat).

Fuel is a relatively simple matter of taking gasoline from the fuel tank and moving it through fuel lines to the carburetor(s) or fuel injectors. And, perhaps more importantly, making sure that the carburetor(s) or fuel injectors introduce the proper amount of fuel to the motor (but that is a subject for another day).

Spark, is exactly what it sounds like. The small electrical flash of lightening that occurs between the center electrode and the tip of the spark plug (clever name eh?) each time that cylinder needs to produce power.

Spark is the final result of your engine's ignition system at work. The lack of it, will keep a motor from starting. Weak spark, or spark at the wrong time, may lead to hard starting or might cause a motor to bog down under load.

The good news is that all modern marine engines utilize forms of a high-energy, electronic ignition system. What does this mean? Well, the fact that there are no points to adjust (except on 20+ year old outboards that we can now lovingly refer to as antiques and only a handful of stern drive motors used into the early 90s, and many of these have since been converted to electronic ignitions) means the systems are stronger and more reliable. As a matter of fact, whereas ignition systems used to be the MOST common cause of engine trouble, they are much less likely to be the culprit these days.

Although complete ignition system troubleshooting must occur with the use of an appropriate manual (such as one for your motor published by Seloc), there are some basic things you can check if you have trouble with your motor.

The first thing to do is get yourself a decent spark plug socket, ratchet and the smallest possible extension you can use. Avoid longer extensions, u-joints or wobble adapters which could put a shear force on the spark plug, breaking it off in the cylinder (which would lead to a very bad day).

Now that you've got your socket and ratchet, remove ONE of the spark plug wires (NEVER remove them all unless you've carefully tagged them before hand) and carefully loosen the spark plug. Remove the plug from the cylinder and inspect it. It is sort of like the thermometer of the motor, giving you an indication of what has been happening.

If the tip is completely soaked with oil or fuel, you know that it may not be firing, but it may also not be the fault of the ignition system. If the tip is black and sooty, but dry, then the motor is running a little rich, but it HAS been running. Grey spark plug tips tell you the motor has been running correctly, while white hot, blistered tips or melted ceramics means that your spark plug is of the incorrect heat range or perhaps that your fuel system is jetted WAY too lean (but again, that's a subject for another day).

Now if your motor was not trying to start (I'm not talking about refusing to spin, since that's the job of the starter motor, but I'm talking about not trying to catch, a little badum-dum as it spins, like it wants to start but just isn't), you want to make sure the tip is at least clean and dry. If so, then the next thing you want to check is whether or not the motor is actually making spark.

The BEST method for this is to use a spark checker. Inexpensive ones are available from your local marine or automotive parts store. They look a little bit like a spark plug, though usually with a threaded adjustable gap and a pair of spring-loaded jaws that clamp onto the motor.

You see, the idea is to install the spark plug wire onto the back of the checker, just like you would to the spark plug itself. Then you install the checker (using the clamp) somewhere on the cylinder head (but not TOO close to the spark plug hole in case fuel is sprayed from it, unless make sure you reinstall the spark plug back into the head for safety before checking). Then, with the gap adjusted to approximately the same as specified for your motor's spark plugs (check your old plug for a rough estimate if you don't have a manual handy), you crank the motor and look for a bright, blue spark.

If spark is present, your problems are likely in the fuel system and not the ignition. I say LIKELY because there are other potential problems with an ignition system, incorrect timing, weak spark, etc. For instance, Orange spark at a properly adjusted spark tester usually means trouble in the ignition system. But again, these checks should be made by following the steps of an appropriate manual.

Likewise, if no spark occurs, you've found your culprit. Always check the basic items first. The motor rigging for some boats will prevent the engine from sparking if the safety lanyard is not properly installed. Other motors have an ignition fuse which, when blown or missing will disable the system. Check the basic things first (like the wiring and connectors) before moving on to the more difficult to check and more expensive to fix (like the ignition module or the ignition coil).

Fig 1. The best method to check if your motor is making spark is to use a spark tester

Fig 2. Connect a spark plug wire to the spark tester and then connect the tester to the cylinder head

Fig 3. Before troubleshooting the entire ignition system, perform a visual inspection for loose or corroded connections