Mercruiser 3.0 Coil Too Hot Engine cuts out after 30minutes

[johnkom]

I have a Cranes Cam electronic ignition on my Mercruiser 233. (Love it.) But...I have the points and condenser in the glove box just in case. After all, I boat on a river and getting stranded is not an option.

JK

 

[lognum]

No Title

Pull the positive wire off the coil. Turn ignition to run. Measure the resistance between that wire and the positive battery post and report back.

Bruce,
Hope I measured the resistance right, but I got .00 to.01??
1. Mechanic ran a wire (White) straight from key ignition to coil. (to try and solve issue)
2.Also spliced in purple resistance wire to coil (red going into purple), before harness to engine.
3. Removed original purple/yellow wire from starter and purple resistance wire and tucked it under harness.
4. Sierra coil that requires external resistor in place. Electronic ignition put on (Sierra) 4cyl Mercruiser 3.0 engine.

Second pic shows that he removed the purple/yellow and purple wire from the coil, but only tucked it under the harness.





Thanks

 

[lognum]

Bruce,
Hope I measured the resistance right, but I got .00 to.01??
1. Mechanic ran a wire (White) straight from key ignition to coil. (to try and solve issue)
2.Also spliced in purple resistance wire to coil (red going into purple), before harness to engine.
3. Removed original purple/yellow wire from starter and purple resistance wire and tucked it under harness.
4. Sierra coil that requires external resistor in place. Electronic ignition put on (Sierra) 4cyl Mercruiser 3.0 engine.

Second pic shows that he removed the purple/yellow and purple wire from the coil, but only tucked it under the harness.





Thanks

The same pic, I know. Was trying to show that the original purple/yellow and purple wire connection was only tucked under the harness. I pulled it out in the picture.
Cheers.

 

[bruceb58]

Well, since he put in that white wire, that's your issue. He probably then branching off from there to the ignition module and that is why he was having problems when the resistor wire was in there. Goes to show you, anyone can call themselves a mechanic these days.

Where are the other 2 wires going?

Out of curiosity, what is the resistance of that purple wire to the positive battery post with ignition on?

 

[stonyloam]

Bruce,
Hope I measured the resistance right, but I got .00 to.01??
1. Mechanic ran a wire (White) straight from key ignition to coil. (to try and solve issue)
2.Also spliced in purple resistance wire to coil (red going into purple), before harness to engine.
3. Removed original purple/yellow wire from starter and purple resistance wire and tucked it under harness.
4. Sierra coil that requires external resistor in place. Electronic ignition put on (Sierra) 4cyl Mercruiser 3.0 engine.

Second pic shows that he removed the purple/yellow and purple wire from the coil, but only tucked it under the harness.

Hmmm..... OK what scale did you have the multimeter on? You are only trying to measure about 1 ohm, so you need it on the lowest scale.
OK, so your 1) guy bypassed the resistance wire, and 4) you need external resistance. If that white wire is still in place that is wrong! The purple yellow wire from the starter is what bypasses the resistance (purple) wire during starting. 2) is strange, red wires are unswitched battery voltage, so that wire would have voltage on it all of the time?? So you need to get rid of the white wire and hook up the purple (purple being ignition switched voltage) and the p/y wire back up to the coil+. Now you need to find out what the correct voltage for the module is. Does it take 12 volts or the reduced voltage from the resistance wire?

 

[stonyloam]

OK as best as I can find out that is a Petronix Ignitor. So you need to have the resistance wire in place for the coil. Now that module needs the full 12 volts to operate correctly. Try this: remove the white wire and the red module wire from the coil and splice them together ( this will give you 12v for your module). Replace the purple resistance wire and the p/y wires on the coil + and you should be OK. I hope. One note, if you leave the ignition on the module could burn out because it is not protected as opposed to the IgnitorII which is. Good luck.

 

[lognum]

Well, since he put in that white wire, that's your issue. He probably then branching off from there to the ignition module and that is why he was having problems when the resistor wire was in there. Goes to show you, anyone can call themselves a mechanic these days.

Where are the other 2 wires going?

Out of curiosity, what is the resistance of that purple wire to the positive battery post with ignition on?

Bruce

This happened (engine quits after thirty minutes) before he put the white wire to the ignition in and before he spliced in the red wire to the purple wire, before the harness. He thought this would remedy the situation, but it only added confusion. When it was about to stall, he spliced in that red wire to the purple one. It kept going and he thought, "well that's it" and left. I took the boat out and it did it again. He then ran a wire (white) straight from the ignition at the key, direct to the coil. That was no better. I always maintained that something was heating up and then cooling down. The coil get's extremely hot and the engine quits till either the coil cools or the electronic ignition cools. Sooo flippin frustrating. I am not electrically or mechanically inclined. Which is why I look to you good folks for assistance. There has to be a remedy, as multiple people in this forum have the same issue.

The other two wires; grey negative from harness, black negative from electronic ignition
Will have to check the resistance on the purple wire.
I did the previously resistance check (white wire to positive post on battery) at a setting of 20 on the voltmeter.

Still needing your help

 

[lognum]

Hmmm..... OK what scale did you have the multimeter on? You are only trying to measure about 1 ohm, so you need it on the lowest scale.
OK, so your 1) guy bypassed the resistance wire, and 4) you need external resistance. If that white wire is still in place that is wrong! The purple yellow wire from the starter is what bypasses the resistance (purple) wire during starting. 2) is strange, red wires are unswitched battery voltage, so that wire would have voltage on it all of the time?? So you need to get rid of the white wire and hook up the purple (purple being ignition switched voltage) and the p/y wire back up to the coil+. Now you need to find out what the correct voltage for the module is. Does it take 12 volts or the reduced voltage from the resistance wire?

Stonyloam,

Mutlitmeter was on 20. When you say module, do you mean the coil? If so, it says 12v on the actual coil, but use with external resistor. Electronic ignition is used with this and it is from Sierra for a Mercruiser 120 serial number A635702. Thanks.

 

[lognum]

OK as best as I can find out that is a Petronix Ignitor. So you need to have the resistance wire in place for the coil. Now that module needs the full 12 volts to operate correctly. Try this: remove the white wire and the red module wire from the coil and splice them together ( this will give you 12v for your module). Replace the purple resistance wire and the p/y wires on the coil + and you should be OK. I hope. One note, if you leave the ignition on the module could burn out because it is not protected as opposed to the IgnitorII which is. Good luck.

Thanks. Would never leave ignition on.

 

[stonyloam]

With the multimeter on 20 you should have read something over 1 ohm. The resistance wire runs from a connector on the electric choke to the + terminal of the coil. To measure correctly: you would remove the wire from the coil, with the key OFF, put one probe on the choke connector and the other on the end of the purple wire. Read the resistance on your lowest scale, probably 20.

 

[lognum]

With the multimeter on 20 you should have read something over 1 ohm. The resistance wire runs from a connector on the electric choke to the + terminal of the coil. To measure correctly: you would remove the wire from the coil, with the key OFF, put one probe on the choke connector and the other on the end of the purple wire. Read the resistance on your lowest scale, probably 20.

The measurement of resistance I measured was from the white ignition to the positive battery terminal. I will measure the resistance you just advised and let you know. The coil is supposed to get 12v at start up and then reduced afterwards. I did measure the voltage when the key was on run, at the coil. It measured 8-9 volts.

 

[bruceb58]

I did measure the voltage when the key was on run, at the coil. It measured 8-9 volts.

That is what it is supposed to be with a resistor in there.

When you measured resistance, you did take the wire off the coil when you measured it right?

 

[lognum]

That is what it is supposed to be with a resistor in there.

When you measured resistance, you did take the wire off the coil when you measured it right?

Yes. I took the white wire off the coil and measured the wire against the positive battery post, for resistance.

 

[stonyloam]

The measurement of resistance I measured was from the white ignition to the positive battery terminal. I will measure the resistance you just advised and let you know. The coil is supposed to get 12v at start up and then reduced afterwards. I did measure the voltage when the key was on run, at the coil. It measured 8-9 volts.

Couple of measurements to make: voltage between the two battery terminals, and voltage between the end of the white wire ( key on) and a good engine ground. They should both read the same, somewhere around 12.8 volts for a fully charged battery. Yeah the coil gets full battery voltage at startup (will be less than 12 v because of the large current draw by the starter) and when the key returns to run, the coil gets reduced voltage through the resistance wire.

 

[bruceb58]

Couple of measurements to make: voltage between the two battery terminals, and voltage between the end of the white wire ( key on) and a good engine ground. They should both read the same, somewhere around 12.8 volts for a fully charged battery. Yeah the coil gets full battery voltage at startup (will be less than 12 v because of the large current draw by the starter) and when the key returns to run, the coil gets reduced voltage through the resistance wire.

The voltage at the coil depends on if the pertronix switch is closed or not. If its closed and there is a resistor wire in there, it should 8V.

That's what he said he measured before in his post #31.

 

[lognum]

Have to look at the boat this week, but haven't made it there yet. Will advise requested info soon. Read on another forum in iboats that Ignitor II solved the same type of issues; http://forums.iboats.com/forum/engi...utdrives/9949738-warm-motor-won-t-start/page3

 

[lognum]

Can the Sierra Electronic ignition be faulty and cause the coil too heat up in any way, or is it only the other way around?

 

[stonyloam]

The voltage at the coil depends on if the pertronix switch is closed or not. If its closed and there is a resistor wire in there, it should 8V.

That's what he said he measured before in his post #31.

The white wire should have been removed from the coil, so it should read battery voltage from the ignition with the key on. The resistor wire will be getting voltage from the choke connector and will not be in the circuit.

 

[bruceb58]

The white wire should have been removed from the coil, so it should read battery voltage from the ignition with the key on. The resistor wire will be getting voltage from the choke connector and will not be in the circuit.

Having the wire disconnected when measuring voltage tells you basically nothing. It's going to measure battery voltage.

2 measurements have been made that contradict each other. He measured basically 0 ohms between the white wire while disconnected and the positive battery post. He measured 8 volts at the coil with the key on. If he really had 0 ohms, he should have measured 12V at the coil.

At this point he needs to follow that white wire and see what it is connected to. He has made as many measurements as he can do and nothing is conclusive.

 

[stonyloam]

Correct we are arguing the same point. He should read 0 ohms between the white wire and the battery +. The fact that he was reading 8 volts at the coil with the white wire attached is a concern. Need to know if there is 12 v on the white wire with the key on, when it is not attached to anything. If he has 12 v there then he can go ahead and splice that white wire to the red wire from the electronic ignition module (make sure you have 0 volts with the key off). Then reattach both the y/p wire and the purple resistance wire to the coil +. At that point it should be wired correctly.