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
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
This product was added to our catalog on Saturday 22 November, 2008.