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Mercruiser MCM 170 no spark wont start

J

jwgroff05

New member
I am the owner of a mercruiser mcm 170 and I cannot get my boat to run at all. I have replaced the battery, the ignition cylinder in the dash, replaced the ignition coil, replaced the rotor, the points, the condenser, the rotor, the distributor cap, the spark plug wires, the spark plugs, the starter, the starter solenoid, and the slave solenoid and I cannot get spark , nor can I get it to start when I do it the old fashioned way of a screwdriver to the starter, of course I dont get spark. I have the points gapped correctly, and the spark plugs are gapped correctly. I have tried everything and I am at a loss and dont know where to go from here. The engine is in great shape I just cant get spark or it to start. The fuel system works great, the trim pump works good. I am out of options and need some HELP.
 
Do you have voltage at the + side of the coil, if yes procede

Remove all the wires on the neg side of the coil. using a jumper to ground with the key "on" scratch the wire to ground. You should see spark from the coli lead. if yes, procede

put a test light on the wire going into the dist and apply power to the light .It must blink as you crank the motor . If not check you work on the points and condensor. If it blinks .you should see spark from the coil when cranking
If yes, procede

Check the rotor, sometimes they will short out to the shaft and kill spark from the dist.
 
Bt Doctur said:
Do you have voltage at the + side of the coil, if yes procede

Remove all the wires on the neg side of the coil. using a jumper to ground with the key "on" scratch the wire to ground. You should see spark from the coli lead. if yes, procede

put a test light on the wire going into the dist and apply power to the light .It must blink as you crank the motor . If not check you work on the points and condensor. If it blinks .you should see spark from the coil when cranking
If yes, procede

Check the rotor, sometimes they will short out to the shaft and kill spark from the dist.
Click to expand...


I do not have any readout at the positive side of the coil. i will look into it an update as I got. thanks
 
To test the coil with voltage applied to the + side you hook a wire to the neg side and quickly touch and remove it from a ground point. It will produce a spark from the coil if the coil and voltage are good.
 
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