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No Spark 1975 25 HP Johnson

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Michaelpaul

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I have a 1975 25 HP Johnson with an elcetric start (key ignition). This motor has always run like a champ. Never a problem. Always starts in a split second. I have not run the motor for about a month, and today I go to start the motor and no spark on either plug. I am sure I am grounding it properly. I am wondering if there might be some type of grounding issue? The motor turns over great, but will not start. Seems to be getting good fuel, but no spark. Any ideas?
 
Re: No Spark 25 HP Johnson

If you're absolutely sure you have no spark..........

There is a black wire leading from one set of points up to one of the "M" terminals of the ignition switch and another black wire leading from the other set of points to the other "M" terminal of the ignition switch.

When the key is in the OFF position, the two "M" terminal are connected within the switch effectively shorting out the ignition, BUT with the key in the ON or START position the two "M" terminals are not connected within the switch which allows the ignition to engage/function.

To test the switch for shorts, simply unplug the cable at the engine that connects the engine to the key switch. Remove the spark plugs and test for spark. If you now have spark, replace the ignition switch.

If still no spark, you may simply have dirty points.... check and clean them with lacquer thinner or acetone.

Still no spark.... the driver coil (under the flywheel) may have failed. cracked open, etc.

If you find that you do have spark and the engine still won't start, suspect that the carburetor needs cleaning.
 
Re: No Spark 25 HP Johnson

JoeReeves - Thank you for your help. I will try the things you suggest. Will I be able to start the engine with teh key or will I haev to try and pull start it with a rope. If I get it started I should be able to shut it off with the manual choke - right? Thank you again!
 
With the main cabl;e unplugged, the key switch no longer has any effect upon the engine.

Yes, you can shut the engine down with the choke if necessary.
 
Joereeves,

I want to make sure I understand you corrrectly. If I unplug the main cable at the engine (the key switch will have no effect) I should be able to pull start the engine - correct. Or at least pull it enough to see if I have spark - correct? I will probably not get a chance to try these things until saturday.

Thank you.
Micahaelpaul
 
That is correct. The key being turned to the off position or shorted out would kill the ignition. Disconnecting the wiring harness (main cable) from the engine eliminates the harness, key switch etc. The engine's ignition system is in effect.
 
Hey Joe,

Guess What? I had my pontoon taken out today for winter storage. Before I took it out of the water I tried to start it again, but it would not start. same thing. Cranked over fine but would not start, with what appeared to be a lot of fuel exiting the exhaust just like before. So when I got it home and placed it on the blocks, as I was planning on working on it today, and before I hooked up a water supply for cooling, I thought what the heck I'll try and start it again (mostly out of frustration). I turned the key and the engine fired right up in a nanosecond! I was very surprised and I quickly turned the key into the off position. Funny thing... the engine did not shut off! It started revving up because I had the high throttle on and I was freaking out. Luckily I chocked it full and it turned off. Then I hooked up a water supply and started many times, but each time it would not shut off with the key. Had to chock it to get it to shut off. I checked the spark and I had good blue spark. I assume from this - much as you surmised - The inginition switch is no good. Thank you again for all your help!!!
 
The ignition switch has two "M" terminals which is the kill circuit.

Key in OFF position = The two "M" terminals make contact within the ignition switch, shorting out the ignition circuit.

Key in ON position = The two "M" terminals are separated, not making contact which allows the ignition to be engaged.
 
You need to remove the ignition switch ( or remove wires ) and do the testing.--------------------------------Your problem could be in the wiring.-----------------Testing is the way to go.-------------Across M terminals should be " open " with key on and " closed " with key in off position.---------------Never replace parts without TESTING.
 
You may also need a new waterpump at this point too. Once you get the ignition fixed, make sure it does not overheat on you.
 
Re: No Spark 25 HP Johnson

Hello Joe,
I had a similar issue as this (on my 1975 25 HP Johnson) and just replaced my iginition switch with a momentary on switch (wire from the battery (B terminal) on one side of the switch and the wire from the solenoid ( S terminal wire) to the other side of the switch). I did not hook up the choke solenoid. Next I took the 2 black wires from each set of the points and ran them to a toggle switch (one per side of the switch). I have not yet tried to kill the motor by using the toggle switch yet as I wanted to verify that this should kill the engine. I have not ran any form of ground to the switch, is that correct? As I read your entry below, putting the two wires from the points together (essentially each post on my toggle switch is now an M terminal) will shut the motor off correct? The other wiring works great, push the button and the motor fires up (choked to kill until I verify if I have this toggle switch wired correctly).

Thanks,
Mike

joereeves said:
If you're absolutely sure you have no spark..........

There is a black wire leading from one set of points up to one of the "M" terminals of the ignition switch and another black wire leading from the other set of points to the other "M" terminal of the ignition switch.

When the key is in the OFF position, the two "M" terminal are connected within the switch effectively shorting out the ignition, BUT with the key in the ON or START position the two "M" terminals are not connected within the switch which allows the ignition to engage/function.

To test the switch for shorts, simply unplug the cable at the engine that connects the engine to the key switch. Remove the spark plugs and test for spark. If you now have spark, replace the ignition switch.

If still no spark, you may simply have dirty points.... check and clean them with lacquer thinner or acetone.

Still no spark.... the driver coil (under the flywheel) may have failed. cracked open, etc.

If you find that you do have spark and the engine still won't start, suspect that the carburetor needs cleaning.
Click to expand...
 
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