how to test a coil??

my son has a 1979 140 merc inboard with a 140 merc outdrive how can we test a coil to see if it is bad. not gettin any fire from coil wire to dist. cap. thanks for any help.









1985 1710-LIL BASS

1986 2150-BAYLINER BLUES

Re: how to test a coil??

Ayuh,... In the Adults Only section,... Download the factory Manuals for the motor,+ drive....
It's all explained in the Manual....

Re: how to test a coil??

Check for voltage on pos. terminal of coil, key on. If yes then while son holds coil wire crank engine, if he doesn't yelp then you have a bad coil.

Re: how to test a coil??

a70 That must be a northeast Ohio proceedure but it only works once. after that you need a new helper and someone to pry mom off your back.

Re: how to test a coil??

how can we test a coil to see if it is bad. not gettin any fire from coil wire to dist. cap.

Click to expand...

Everybody always wants to blame the coil when they don't have spark, probably 99% of the time the only problem is glazed over points.
A quick check would be to get a points file and clean the points and recheck for spark, if you have spark then, put in new points and do the full tuneup

Re: how to test a coil??

i have pulled wire from coil off of dist cap and there is no fire from coil to cap.so would that not mean you would have no fire from points if there is no fire from coil. oh and son is told old for that i already got him when he was younger.

Re: how to test a coil??

have pulled wire from coil off of dist cap and there is no fire from coil to cap.so would that not mean you would have no fire from points if there is no fire from coil.

Click to expand...

Ayuh,...

Point fired ignition 101,...

The Coil has 3 wires,...
The (+) which is the 9V or 12V Primary side...
The (-) which is the negative Primary side...
And the High-tension lead to the distributer cap center...

The (-) Negative side of the coil is wired to the Points, located in the lower section of the distributer...
When the points Close,.....
The Coil is Grounded on it's primary side,... Which fires the 2ndary side, aka. the High Tension lead...
Which of course goes to the top of the distributer, to whichever sparkplug is firing...

I think you're confusing the Primary,+ Secondary sides of the system...
The Points fire the Coil....

Did you download the Manual for it yet,..??