1981 mercury 80hp no spark

[roxi]

I am new to site and need ideas as to 1981 mercury 80 hp no spark #4 cyl. I swapped coils #3 and #4 still no spark #4 but #3 had spark this tells me coils are good ; could this mean switch box is bad or are there other tests to narrow down problem. Also if I buy a used switch box is there any way to tell if it is good.

 

[CharlieB]

Re: 1981 mercury 80hp no spark

If all three other cyls fire consistantly it is not a trigger or stator issue and most likely the switchbox,

HOWEVER, since there is NO RETURN on electrical parts, this SHOULD BE VERIFIED with DVA testing.

A used switchbox MAY work, but what guarantee do you have? None.

I tell a lot of V6 owners to hang onto a 3 cyl switchbox that has a bad Bias circuit as it will work fine on a 3 cyl motor.

BUT, the just ain't very many v8's that you will find a 4 Cyl switchbox. I would not trust a used box, get a NEW CDI or Sierra, AFTER verifying the 'no output' on your switchbox with a DVA meter..

 

[roxi]

Re: 1981 mercury 80hp no spark

thanks for the reply. Could you explain the test process I have ac/dc multi meter will that do the job if so what connections do I read and what is the voltage reading

 

[CharlieB]

Re: 1981 mercury 80hp no spark

You will need a DVA adaptor, which will work with any volt meter, to properly load the component which will cause the system to raise voltage and hold it in a capacitor long enough to for a meter reading. A volt meter alone will only show a 'blip', even the peak reading digitals will not read with any accuracy without the DVA adaptor.

The adaptor is quite simple and parts are cheap, directions for a DIY can be found posted here

http://forums.iboats.com/showthread.php?t=374544

CDIElectronics has a free Ignition Troubleshooting Guidie available on their Support page, the Guide lists all outboard ignitions, test values and specific test per each ignition to positively diagnose any problem quick and easy, once you build or buy an adaptor.