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No spark 1968 Johnson 40Hp

T

turbowrenchhead

Member
Good morning and hello. I'm a new member as of today. Thursday I picked up a 15' Fiberglass starcraft and a 1968 Johnson. The seller stated that the motor did not start and it probably needed a starter and or a solenoid. I am a mechanic so I checked out the motor to make sure it wasn't a dud. You can never trust what ppl tell you, that I have learned the hard way. So I brought some tools and a compression gauge. The compression was at 105psi on both. So that was a little low but live-able. Next I checked for spark and it had it. I shot a bit of starting fluid into the carb and it started for a couple seconds. So I bought it. I took it home and pulled the starter and solenoid and took it to a rebuild shop. They said nothing was wrong with the starter so they put it back together and sold me a solenoid and charged me $25. I put the starter and solenoid back on and now had a freshly charged battery. I cranked over the engine and I had no spark. I started looking it over and I came across a wire that was disconnected and I didn't remember disconnecting it from anything. After many hours of reading and downloading a manual I now know that it was the wire coming off the side of the cut out switch and is suppose to supply the ground to the starter solenoid. Before I knew what was what. I tried connecting it to ground and then to power and I still had no spark. No combination worked, still no spark.
At this point I know that my safety switch is no good. Its always is a closed circuit. So that switch is bad. The previous owner must of had the safety switch and cut out switch bypassed because there is a wire going to the starter solenoid that has constant ground. After studying a wire diagram I tried hooking up power to the coils. Yeah the wire got warm fast. Thats not good! I pulled the flywheel and the RH side coil was warm. I ohmed checked that coil and I had .6 ohms on primary and 4000 on secondary. I would think that this is in spec but I have no parameters to go by.
So my question is how do the coils get there power. Is there battery power supplied to both points and the points control the power side?
I have two black wires coming out of the distributor but I don't know if they are suppose to both have power on them or not. Is white ground and black power??
I'm a auto and atv mechanic however this is a whole new ball game for me. I'm used to stators and cdi's. Those I have no problem diagnosing. Did I fry my coils by supplying power to the distrib? Any help would be greatly appreciated. I thought I was going to be on the water today fishing with my family. That's not happening this weekend.
 
Battery power is not used to make spark in this engine.------------Absolutely stop hooking up wires untill you know for sure what and how thing work.--------Pull the flywheel with the proper puller and inspect ignition coils , the system has 2 independant coils / points / condensers.
 
Then what is supplied to the coils to make a spark? Its certainly not ground. Where do the two black wires go if I don't have a key? I pulled the flywheel and inspected everything. All of it looks like its been replaced recently. I tested the coil that had the points closed when I supplied power to it and the coil got warm. It still ohm's out on primary and secondary.
As I am getting into this more and more I'm starting to understand how it all works. It seems that no one can answer the question of the two black wires and what is suppose to be on them.
 
????-----------I say it again , 12 volts is not used to generate the spark !!!--------This is a magneto and it powers itself !!!-------Something similar to a lawnmover and chainsaw.----Those items have never needed a 12 volt battery to run.-------You now might as well buy 2 new coils too !!!---------No one can answer that question about the 2 black wires ??-------------When the 2 black wires are connected together they ground out the points and the motor stops !!!!
 
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You're right. I should of did my research first but I couldn't find an answer anywhere. I now know that those black wires are a switched ground. When grounded they kill the ignition. I went back to the motor and left the black wires open and I had spark. I shot some starting fluid into into the carb and it fired for a split second and it sounded like just one cylinder did. I went to test for spark again and now there is no spark at all. Next I'm pulling off the flywheel and testing the coils and condensor.
 
I tested the coils. I have .6 ohms on primary and 4100 ohms on secondary on both coils. I did have power supplied to the coils on one occasion. Can the coils still be bad even though the resistance is fine? I also checked the condensors and they both test good. I'm at a loss.
 
Are the coils cracked? Most old ones are. And if they are, they are junk. Otherwise, 90% of no spark problems are due to dirty or corroded breaker points contacts. Completely remove them from the plate and degrease them and individually polish each contact shiny bright. Put everything back together and set points gap to .020" at their widest opening.

When you reinstall the flywheel, the tapers MUST be clean and dry, and you MUST use a torque wrench to tighten the nut to 100-105 foot pounds. Ignore this advice and risk shearing the key and doing serious $$$ damage.
 
BTW, the kill switch connects the two black wires together to stop the motor---not to ground. Well ok, to ground would do it also, but why re-invent the wheel?
 
All the distributor parts look newer. Unless this was stored in a climate controlled storage for its entire life. Not likely in Wisconsin. The coils have no cracks or signs of failure. I set the points today. I did not remove them. I resistance checked the points with everything disconnected. The resistance check should verify that they are working. One point set looks like the contacts are misaligned. There was no adjustment for alignment so I set the gap on both. However I still had no spark after all the resistance checks and point set.
Good to know that I have to torque the flywheel. I just hit it with an impact at 90psi. I'll make sure to pull it tomorrow and re-torque it.
Thanks fdrgator for the info on the black wires. That will help me rewire this cobbled up mess of toggle switches. I should just get a ignition switch/key and redo it right. Anyone know a of a cheap one that would work for me? It doesn't have to be OEM. Any good aftermarket will do.
In my research today I found that my motor is a 1969 model year and not 68 like it states on the registration card. I do believe that the wire diagrams were any different for the ignition system from 68 to 69. I have a 40E69R model.
I had yet another issue with this pain in my ass. The shifter cable is seized up. I lucked out and found a new shifter cable for $35 shipped to my door. I seen that most were going from 89-129. Yikes!
Hopefully by next weekend I'll be able to get this vintage ride on the water by next weekend. The fish are starting to bite now after the heat has died off. I'm getting antsy to go fishing!
Thank you to all for the info! Keep it coming. I like to learn about machines. This is my next challenge!
 
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I have spark now! I had both wires coming off of the dis together so I could shut it off if I had too. Now it all makes sense. I pulled those apart and I went back in and cleaned the points, set the gap, ohm tested the coils and the plug wires. Everything tests good. Put it all back together and torqued the flywheel to 100's. Cranked it over and yay, spark!
Now I have a spring that is attached to the recoil cover and I don't remember where the other end goes.
 
Assuming you mean the spring in the recoil starter lockout. Upper end goes in a small hole in a web on the casting, lower end hooks in a little tab that slides up and down on the round lockout rod.
 
Our host, marineengine carries the Sierra Marine line of ignition switches, but a quick look doesn't find any that aren't special order. mp39040 (brass) would be closest to original. mp39830 (plastic) similar. mp39090 (plastic) similar with push-to-choke function. You might take these numbers to a local marine dealer.
 
Thanks kincrwbr1! After looking at a parts fiche I figured it out. The pics confirms that I got it right. I put the motor all back together and wired it and it took off with a couple of squirts of the starting fluid. It seems to run good however when I try to rev it in neutral it won't rev. Like there is a limiter on it. It seemed fine in F or R but I couldn't rev it much because it would of launched the trailer off of my jack stands. I need a taller barrel. I only have a shorter one and I had to prop the front end of the trailer up to get the motor submerged. So is this motor suppose to rev in N?
 
Do not attempt to rev it in neutral or a bucket. There is a vacuum cut-out switch to prevent that. If the switch isn't working, and you do manage to get it to rev, it may go into run-away mode, and you can't slow it down. Maybe I should have called it panic mode, because you certainly will panic when that happens. The motor was designed to run on a boat, on the lake.
 
I worked on my boat most of the day today and got everything ready. My son and I went out on the lake for an hour. It started right up and ran good. I did a full throttle run for 5 min and ran great. Stopped and did a bit of fishing and then went to head back and went to go full throttle again and it disengaged while in gear as soon as there was a load on it. I'm clueless to what it could be. Any suggestions?
 
There a a ton of props on Ebay. The part # 0378581 is obsolete and isn't available. Its 10-3/8 x 11. The superseded part # is
0385955 and is 10-3/4 x 11. I would assume that this one will work for me. I found one on Boats.net for $108+shipping. How are props measured? ​
 
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