78 merc 115 intermitant spark

[Davem1754]

My 78 loses spark at any given time, motor will start and run fine, then when I go to restart, it sometimes has no spark.
I have replaced the brain module, ignition coil, and replaced all bad wiring.
I removed the distributer for inspection, but could really not check for any bad connections because the wires were all sealed.
Is there a test I can do with a voltmeter for the distributer?
Any other suggestions that would help me pin point this problem?
Many thanks in advance.
Dave

 

[Chris1956]

Re: 78 merc 115 intermitant spark

Dave, There is a test for all components but the trigger. It is posted on the CDIElectronics.com web page.

When I had your issue on my '77 Merc IL6, the trigger was intermittent for a while, and then failed. Hope you have better luck.

 

[Davem1754]

Re: 78 merc 115 intermitant spark

I was told by a local marine dealer that my motor does not have a trigger, just a stator under the flywheel with its only purpose is to charge the battery.
If this is not correct, where is the trigger located?
Many thanks,
Dave

 

[jheron]

Re: 78 merc 115 intermitant spark

Hi Dave,
Your TOP has a trigger thats triggered by a disk with holes cut into it on the base of the distributor. The dealer is dead wrong.
There is a carbon brush and spring under the distributor cap that can get gummed up and cause you problems. Clean up everything with some degreaser and sand paper and lightly oil it with some fine machine oil and give it a go. If you still have grief heed Daves advice and look into the trigger...
Cheers,
Jon

 

[CDI Tech Support]

Re: 78 merc 115 intermitant spark

Dave, There is a test for all components but the trigger. It is posted on the CDIElectronics.com web page.

Actually, there is one test for the trigger:

Mercury 4 and 6 Cylinder - 332-2986

under "No Spark On Any Cylinder"

5. Check DVA voltage between the White and Black trigger wires (they must be connected to the switch box). You should read at least 3V. A low reading indicates a bad trigger.

 

[CDI Tech Support]

Re: 78 merc 115 intermitant spark

I was told by a local marine dealer that my motor does not have a trigger, just a stator under the flywheel with its only purpose is to charge the battery.
If this is not correct, where is the trigger located?
Many thanks,
Dave