1979 80HP Mercury - Not Firing on 2 cylinders

[sramelyk]

I've done quite a few repairs on this motor and feel like I have a pretty good understanding of where I've gotten to in my troubleshooting so I guess you'll need to trust me some.

I've isolated the problem to the stator/trigger or switchbox. Which leads me to my question..

I'm having a hard time testing the stator. I've followed the procedures in my book but don't feel like I'm doing the ohms test correctly. I have an associates degree in electronics and know how to use a meter and know how to measure ohms.

Anyways.. Instead of fighting with the stator, is it safe to say that since I only have 2 cylinders not firing its probably the switchbox? I thought that if the stator/trigger was bad it would be all the cyclinders.. Is this a safe assumption?

 

[CharlieB]

Re: 1979 80HP Mercury - Not Firing on 2 cylinders

The stator is an AC Generator, if you have good spark on any cyl then the stator is most probably good.

The triggers are small AC Generators that signal the ignition module when to discharge the capacitors.

'No Spark' on two cyl's could be a fault with either the trigger OR the module.

Since there is NO RETURN on electrical parts it is imperative that proper testing be done to RULE OUT proven good components.

DVA testing of the stator and triggers is the most reliable method of testing, the DVA Meter or DVA Adaptor with a VOM places a measured load on the AC Generator and stabilizes the meter to make an accurate reading possible.

CDI Electronics.com have a very detailed Outboard Troubleshooting Guide available for FREE download. Their guide will direct you to the proper sequence of test, both DVA and Ohm's for your model.

Also, a bad rectifier can skew spark tests in that the disruption of the magnetic fields within the flywheel/stator CAN and WILL obscure cranking tests.

Disconnect the yellow stator wires from the rectifier and retest for spark. Leave the wires disconnected for cranking DVA tests of the stator and triggers.

Repost with your findings and/or any other ????'s you may have.

 

[sramelyk]

Re: 1979 80HP Mercury - Not Firing on 2 cylinders

Thanks. Downloaded the guide.. Had some experience with testing the electrical system before and this guide added to that..

Problem fixed. Was a corroded trigger wire (To the point of nothing) under the flywheel. Bandaided it with a new wire till I can afford trigger kit.

Thanks for the help.