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1990 mercruiser 5.7 ignition problems

Z

Zlang122

New member
Hello I have a 1990 mercruiser 5.7 thunderbolt, I have lost all spark, so far I have changed the ignition module, the cap and rotor and tried a new coil but no change, I have a feeling it could be the points are closed and need to be reset, but I don't want to go further without some other input first, any advice or Input is greatly appreciated. Thank you in advance!
 
What do you call the ignition module?

If you feel the "points" may be bad that would tell me you did not take off the distributor cap??? As said this is electronic and no points.

If you did you would have seen a rotor assembly (two piece assembly with rotor and steel toothed flag attached to the rotor) and the teeth of the steel part move through the sensor pick up or what is called the Sensor assembly.

What I suspect is you are referring to the timing module. That is where the wires from the distributor connect to.

Typically if you have no spark but have 12 volts to coil the SENSOR assembly is bad. Not always but typically.

Here is a link to the parts break down. May not be the specific year but the parts are the same

http://www.marineengine.com/parts/m...-0f600999/distributor-and-ignition-components



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 which the other end is connected to ground. Remove the white/green lead from the dist. terminal. Turn the ignition key to on and strike the white/green (this is the timing module wire not the wire from the distributor)lead to ground. If there is spark, replace the ignition sensor assembly inside distributor.

#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.
 
Thank you all for the input, I am away from the boat today and will check all the things as soon as I get back! I am not real familiar with this ignition system so everything you all are telling is just making all make more and more sense. Thanks I will let yall know if these things lead to a solution.
 
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