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1975 20 hp Merc with Ign. problems?

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b_tomtom31

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I have a 1975 20 hp merc. We are not gettin good fire to the spark plugs, we put a tester btw the wires and the plugs and it is real spotty but we know fuel is getting to the chamber. sometimes it will only spark once in 15 secs. It wont run now, only fire off occasionally with elec. start. the plugs are good, we rebuilt the wires, the coils look good. Do you have any ideas for us before we buy another switch (power pack) or stater? Do you know if there is a way to test the power pack? Thanks, Brian
 
The trigger coil and stator can be tested with an ohm meter, so look at them first. If any circuit is open, it's toast. The sparkbox needs special testing equipment.

Jeff
 
Make sure "kill" button is operating. The orange kill wire is the ground to this ignition, you can ground the orange wire to the engine block and retest, if it sparks your button is bad or not making connection(normally closed to run ,open to kill)
 
Also, We are not getting any spark to the coils now. They test at 0, all the time. We have 15 volts on the wires going into the power pack so the stater is working.
 
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Make sure "kill" button is operating. The orange kill wire is the ground to this ignition, you can ground the orange wire to the engine block and retest, if it sparks your button is bad or not making connection(normally closed to run ,open to kill)
Click to expand...
This is for the 1975 phasemaker ignition which as a red oval ignition plate under flywheel.
 
I hope not! The PhaseM aker monstrosity was 71/ 72. By 75 they had the modern system with the black box.

Is that what you have?

Jeff
 
Spark Box.jpg

This is what the switch box looks like. I am pretty sure that the motor is a 1976, now. I apologize for the mixup. Thanks for all the help. I found a used switch box on ebay for $50 so I went ahead and bought it. We are going to make the swap since we know the stater is working. If it still doesnt get fire then we will go from there. Is there a wiring diagram for this? Where? Part#332-4911A2
 
Good deal! That is NOT the dreaded Phase Maker; it's the newer type black box.

I hope that does it for you.

Jeff
 
Ok guys, I need some more help.

We got the used switch box and put it on. We are getting 20V on the high side from the stator and 36V on the low side. per the chart, these readings are off. What might be the problem?

We did go from 0V reading on the wires to the coils with the old box to 3V now that we have switched them. Actually, one wire is now reading 3V consitently and the other is reading btw 1V & 3V fluctuating.

Any ideas?


guyjg said:
use this chart for reference http://www.outboardignition.com/page39.asp No trigger = no spark Stator out of tolerance =no spark. Pull the flywheel if the readings are off; you may find bad wiring.
Click to expand...
 
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ITS RUNNIN!!!

Problem was in the kill switch wiring. Thanks for all the help.

Part #332-4911A2 for sale $60 +shipping. I am in Cumming, GA 30040

Thanks again. Brian
 
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