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mercruiser 4.3 lx not starting

Try this.

Tests for Thunderbolt Ignition:
W/ignition key on AND BILGE WELL VENTILATED OF GAS FUMES!!!

#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.

#2 - If 12 volts is present, remove the coil spark wire from the distributor and connect it to a spark gap tester to ground. Remove the white/green lead from the dist. terminal. Turn the ign. key to on and strike the white/green lead to ground. If there is spark, replace the ignition sensor in the dist.

#3 - If there is no spark, substitute a new coil and repeat test #2. Now if you get spark, install a new coil. NO SPARK, replace ign. amp.

#4 - In #2, if there is No voltage present, disconnect the white/red wire and check it again for 12 volts. If 12 volts is present, replace the ignition sensor inside the dist. cap. If no 12 volts present w/it disconnected--ignition amplifier is shot and must be replaced."
 
I did the ignition testing wrong Ill have to do it again today and let you guys know. there is one thing I am confused about
#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.
there it says connect to red white wire at the dist to check this I need to disconnect the wire? because the next step says to disconnect and test again. or should I just push my probe through the wire insulator to see if i get voltage or not. that kinda is confusing me. sorry if i sound dumb i just want to make sure I follow the steps correctly
 
It's usually a gray wire. There will be two wires; one goes to the ignition amplifier and the other goes through the engine harness to the tach.
 
I did the ignition testing wrong Ill have to do it again today and let you guys know. there is one thing I am confused about
#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.
there it says connect to red white wire at the dist to check this I need to disconnect the wire? because the next step says to disconnect and test again. or should I just push my probe through the wire insulator to see if i get voltage or not. that kinda is confusing me. sorry if i sound dumb i just want to make sure I follow the steps correctly
 
#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.

#2 - If 12 volts is present, remove the coil spark wire (This is the center wire on the distributor cap) from the distributor and connect it to a spark gap tester to ground. Remove the white/green lead from the dist. terminal. Turn the ignition. key to on and strike the white/green lead to ground. If there is spark, replace the ignition sensor in the dist.

#3 - If there is no spark, substitute a new coil and repeat test #2. Now if you get spark, install a new coil. NO SPARK, replace ign. amp.

#4 - In #2, if there is No voltage present, disconnect the white/red wire and check it again for 12 volts. If 12 volts is present, replace the ignition sensor inside the dist. cap. If no 12 volts present w/it disconnected--ignition amplifier is shot and must be replaced."
 
Docksidemarineservices said:
#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.
Click to expand...

ok again there is no way to test my red white wire unless I disconnect it so my question is do i need to disconnect it to test? my ignition sensor is updated you can not see the wires inside the dist unlike the older version. there is no way to test it unless i poke through the wire insulator. so do i need to disconnect the quick connect to test?
 
After doing #2, if there is No voltage present, disconnect the white/red wire and check it again for 12 volts. If 12 volts is present, replace the ignition sensor inside the dist. cap. If no 12 volts present w/it disconnected--ignition amplifier is shot and must be replaced."
 
but how do i do test number one where do i test at? there is no way to test the red and white wire at the dist there is no metal wire showing only at the connector and i have to disconnect it to test it
 
ok here are the results from the test first off the battery is only at 11.5 volts. with the white red wire I had 10.5 volts, then I disconnected the red white and tested again. On the male bullet connector I had no voltage on the female side I had 11.5 volts, reconnected the red white. then disconnected the green white using the male end of the connector and spark tester taped the male end on a ground and got no spark. does this mean I have a bad coil? does it sound like i did the test right so far?
 
You want to tap the green/white wire end that comes from the distributor to ground with the key on to check for spark. Make sure you have a good ground on your spark tester.

You would only disconnect the red/white wire if you had no voltage.
Step #4 is done if you have no voltage in step#2
 
Docksidemarineservices said:
You want to tap the green/white wire end that comes from the distributor to ground with the key on to check for spark. Make sure you have a good ground on your spark tester.

You would only disconnect the red/white wire if you had no voltage.
Step #4 is done if you have no voltage in step#2
Click to expand...

thats exactly what I did and no spark
 
Docksidemarineservices said:
#3 - If there is no spark, substitute a new coil and repeat test #2. Now if you get spark, install a new coil. NO SPARK, replace ign. amp.
Click to expand...

what is the ign. amp.?

My motor is a 95 are you sure it as it? there is not electrical box mounted on the risers the only thing electrical is the shift interrupt switch nothing else at all
 
Last edited:
ok I was going over the mercruiser service manual for my boat and my year motor does not mention anything about ignition amplifier here is the page it mentions nothing about it. this manual is the one for my year boat motor


ignition testing.jpg
 
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