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75hp Johnson V4 no spark

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Blaine Rockey

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Hello, I have a 1960-75hp Johnson V4 outboard with no spark at the spark plugs. Could the coil be bad? How do I check it out? Thank you. Blaine
 
The coil inside the belt driven magneto might be shorted to ground.----Have you cleaned / set the breaker points ?-----Rotor could be shorted to ground.------Coil can be tested using a ----MERC-O-TRONIC ----magneto analyzer.----Have to find a shop with one.----The coil is pricey.-----Your location ?
 
racerone said:
The coil inside the belt driven magneto might be shorted to ground.----Have you cleaned / set the breaker points ?-----Rotor could be shorted to ground.------Coil can be tested using a ----MERC-O-TRONIC ----magneto analyzer.----Have to find a shop with one.----The coil is pricey.-----Your location ?
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Thank you for your reply. The points have been set. Here in Michigan it is becoming difficult to find someone to work on these old motors. Otherwise the motor is clean and looks like it has been rebuilt based on the "newness " of the various gaskets.
 
Well--- these motors are not difficult to work on in my opinion.----Remove the magneto.----Remove the cap.----See if coil is visibly in good condition.-----Spin the magneto by hand and see if spark comes out of the coil.-----This magneto powers itself.----There is no need to hook 12 volts to it.----Coils are on hand on this very site at $125 each.----Cheaper than they were years ago.----Likely NOS I think.----I have some used parts for these magnetos I think.
 
racerone said:
Well--- these motors are not difficult to work on in my opinion.----Remove the magneto.----Remove the cap.----See if coil is visibly in good condition.-----Spin the magneto by hand and see if spark comes out of the coil.-----This magneto powers itself.----There is no need to hook 12 volts to it.----Coils are on hand on this very site at $125 each.----Cheaper than they were years ago.----Likely NOS I think.----I have some used parts for these magnetos I think.
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Thank you for your help. I will try your suggestion of spinning the magneto for spark. The coil looks to be in good shape. Thanks again.
 
I am having similar problem with my 1964 Johnson but there is spark at the coil and i had just replaced the distributor cap yet im getting no spark at the plugs. Plug wires are reading fine on a multimeter. Points are set to the correct spacing. I think it could be possibly shorting out at the rotor but the rotor is in good shape and not cracked. Any ideas?
 
I have put electrical tape on the rotor shaft before and It did not work could it be anything else or is there anything else I could try? Also do you know a reliable source that I could get a new rotor from the source that I purchased the cap from has them going for 100$ seems pricey for just a rotor.
 
I agree with Racer. The rotor center tab is shorting thru the plastic to the shaft/ground. Defect most likely is not visible.
I don't believe electrical tape will stop 20,000 volts from traveling to ground via the path of least resistance.

You didn't give a model number of the motor. There are 2 types, magneto & battery ignition.
I'm assuming you have battery ignition (with an external "can type" coil & round distributor cap) because you say you have spark at the coil.
Both systems use similar but DIFFERENT rotors. The outboard end of the tab is different between the 2.
It's pay the price or start rowing.
 
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Model number of the motor is v4a-v4al-16d. Part number 580338 for rotor. I have an old parts catalog that came with boat when I bought it.
 
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