'88 Mercury 100 HP Ignition Problems

[agwood75]

I have a 1988 100 HP Mercury outboard. I have replaced the rectifier, stator, trigger and switch box and I still cannot get a spark on any of the 4 cylinders. I plan on replacing the coils, but from what I hear it is not common to have all 4 coils go out at the same time. I have ran all the tests on the rectifier, stator, trigger and swichbox that CDI provided and they all are within range. I noticed in one of the tests provided by CDI it states that you should disconnect the yellow wires from the stator to the rectifier and try to fire the engine. I did this and I got it to fire, so I replaced the rectifier and I still have the same issue. The coils did test out of range, but is it possible for all of them to go out? Does anyone have an idea on where to go next or what to do?

 

[CharlieB]

Re: '88 Mercury 100 HP Ignition Problems

Since you have already replaced most the entire ignition system, I would almost bet that you have NOT disconnected the black wire with the yellow trace from the ignition module to the wiring harness, THEN rested for spark.

OR

Your cranking speed is below the minimum 300 RPM required for the stator to make sufficient voltage to operate the system.

A grounded ignition switch safety lanyard, or short in the wiring harness will very effectively kill the ignition and falsely lead you you believe you have an ignition problem as will a low battery, poor connections, or weak starter.

Hope you haven't thrown away any of the old parts, many may still be good and have value to another boater.

 

[agwood75]

Re: '88 Mercury 100 HP Ignition Problems

I have disconnected the black yellow and I got the same results, the engine will crank but not fire. I started with all of the simple things first, such as checking battery voltage and making sure that the engine is receiving the correct voltage. The RPMs bounce between 250-300 while cranking.

Like I mentioned the engine will fire when the yellow wires from the stator to the rectifier are disconnected, but will not when they are.

The issues started when I was bringing the boat back to the dock. It ran fine all day, but it lost power slightly and then would not fire unless I got the RPM's up over 3000. That is why I suspected the stator or some type of ignition problem. After replacing all of these parts I canoot get it to fire.