Is my charger wrecking my Coil?

[Rinker85]

I have a ship n shore battery charger/maintainer that I have plugged in all the time to maintain the battery. It is not a onboard permanently mounted charger. My coil is bad. This is the 2nd time in two years that I have replaced it. Could the charger be wrecking it?

My engine is a 1985 2.5L OMC.

 

[Bondo]

Re: Is my charger wrecking my Coil?

I have a ship n shore battery charger/maintainer that I have plugged in all the time to maintain the battery. It is not a onboard permanently mounted charger. My coil is bad. This is the 2nd time in two years that I have replaced it. Could the charger be wrecking it?

My engine is a 1985 2.5L OMC.

Ayuh,... So long as the key is off, the coil sees no power...

Donno how yer comin' up with that...

How much voltage is goin' to the coil, with the key On,..??

 

[Rinker85]

Re: Is my charger wrecking my Coil?

Ayuh,... So long as the key is off, the coil sees no power...

Donno how yer comin' up with that...

How much voltage is goin' to the coil, with the key On,..??

10.7 volts

 

[Rinker85]

Re: Is my charger wrecking my Coil?

If I turn the key on or try to start the boat with the charger still hooked up would that ruin the coil?

I have also read that a shorted tach will ruin a coil. My tach stopped working last year but I was still able to go boating. I noticed the coil problem at the end of the year when I tried to start the boat to fog the engine. I'm not sure how to test for a shorted tach. I did disconnect the wires on the tach and hooked them to a portable tach and the portable tach did work.

Any thoughts on this?

 

[Don S]

Re: Is my charger wrecking my Coil?

I seriously doubt a bad tach can kill a coil, might short it to ground, but then the engine won't run. Charger killing a coil, not likely.
If you leave the key on and the points are closed, yeah, that might kill it. A bad plug wire, spark plug or cap that doesn't fire will usually crack a coil tower.

Exactly what kind of coil problems are you finding that causes you to change them?

 

[Rinker85]

Re: Is my charger wrecking my Coil?

I seriously doubt a bad tach can kill a coil, might short it to ground, but then the engine won't run. Charger killing a coil, not likely.
If you leave the key on and the points are closed, yeah, that might kill it. A bad plug wire, spark plug or cap that doesn't fire will usually crack a coil tower.

Exactly what kind of coil problems are you finding that causes you to change them?

Well the engine won't start. I'm not getting spark. I did two different types of tests on the coil and found it to be bad. This is the 2nd one in 2 yrs. I've had the boat for 20 yrs and have never had a coil problem until just recently.

 

[Don S]

Re: Is my charger wrecking my Coil?

What tests did you do?

 

[Rinker85]

Re: Is my charger wrecking my Coil?

What tests did you do?

I pulled the coil wire from the distributor cap and tried to get it to spark to ground while cranking the engine.

I disconnected the negative wire going from the coil to the distributor points. I then put a jumper wire on the negative side of the coil and momentarily touching to ground. This should create a spark from the coil wire to ground and it did not.

I also hooked up a 12 volt test light to the negative and positive of the coil and cranked the engine. The test light should go off and on as the points open and close and it did not.

 

[bruceb58]

Re: Is my charger wrecking my Coil?

I also hooked up a 12 volt test light to the negative and positive of the coil and cranked the engine. The test light should go off and on as the points open and close and it did not.

That's a problem with your points and or connections, not the coil. Measure the voltage at the positive side of the coil with the points open. Should measure battery voltage. Measure with the points closed and it should be closer to 9V. If it isn't dropping to 9V you have bad points or a bad connection on the wire that goes from the coil down to the points.

If you have faulty spark plug wires, a bad cap or plugs with too large of a gap, you will eventually wipe out your coil. What happens is that if any of the previous things are bad, the field that is present in the coil needs to go somewhere and it can't so it finds the path of least resistance which often is through the coils internal structure which then destroys its internal insulation.

 

[Rinker85]

Re: Is my charger wrecking my Coil?

That's a problem with your points and or connections, not the coil. Measure the voltage at the positive side of the coil with the points open. Should measure battery voltage. Measure with the points closed and it should be closer to 9V. If it isn't dropping to 9V you have bad points or a bad connection on the wire that goes from the coil down to the points.

If you have faulty spark plug wires, a bad cap or plugs with too large of a gap, you will eventually wipe out your coil. What happens is that if any of the previous things are bad, the field that is present in the coil needs to go somewhere and it can't so it finds the path of least resistance which often is through the coils internal structure which then destroys its internal insulation.

Thanks for the info. I will try that test tommorrow. What about the first two tests I did? Do the results indicate a bad coil or are there other factors that would lead to the results I got?

 

[bruceb58]

Re: Is my charger wrecking my Coil?

The test where you had a jumper on the negative side of the coil and simulated the action of the points should have produced a spark. Were there other wires on the negative side of the coil when you did that test? I would remove the tach wire from the coil until you figure out what is wrong. A bad tach can cause your problem.

 

[Rinker85]

Re: Is my charger wrecking my Coil?

The test where you had a jumper on the negative side of the coil and simulated the action of the points should have produced a spark. Were there other wires on the negative side of the coil when you did that test? I would remove the tach wire from the coil until you figure out what is wrong. A bad tach can cause your problem.

Well I just did the test again in the quote above with the tach disconnected and I was able to get a spark. So it looks like it's a shorted tach.

 

[bruceb58]

Re: Is my charger wrecking my Coil?

My standard advice applys...It's never the coil. You have probably been battling an intermittant tach and you have always thought it was the coil.