1972 Johnson 100 HP not firing constantly

[57 7.5]

Ok I've posted several different post for this motor and finally got it running. Now I have a new problem, I have all new batteries for starting and trolling, Also have new battery cables to let everyone know. I can go out one day and start the motor and it run fine and start with just a turn of the switch once it warms up. Then I can go out the next day and it won't fire, just turns over. I don't have a spark tester yet but believe i'll get one soon since it seems I need one. I did a compression test and all cylinders have 120 psi except the bottom cylinder on the bottom right it's 110 psi. When it's running the boat (16 ft f/s) will do 40 mph with two people, full tank of gas and all the gear I have stored and one live well full of water. Also have pulled a tube with two people and still got 35 mph. So I'm not sure where the problem is, if it's the coil or the pulse pack, I have a used remanufactured power pack and coil that I got a good deal on just to have in case. Any help would be great.

 

[F_R]

Remanufactured pulse pack, eh? Wonder how they did that. Well anyhoo, it is a possibility that it is the problem, but try to avoid getting into the old "it's always the black box" mentality.

That motor has an ignition system that was state of the art at the time, but now we realize it was ........well I'm trying not to use the word.......crap. Regular maintenance of the distributor under the flywheel is necessary. There is a silver wire anti-reverse spring in there that wears out if not lubricated and the wear dust fouls the distributor, causing the spark to go somewhere other than where it is supposed to. When it wears badly enough, it breaks in two and shorts out the sensor system. So, even if something else is wrong here, keep that in mind.

I don't think I have to tell you, check the spark. Does it have no spark, intermittent spark, or what? You don't know.

Other than the items mentioned, you need to check the input voltage at the pulse pack. nothing in, nothing out.

 

[57 7.5]

Thanks, well wasn't sure about the repaired pulse pack either but has a tag attached that says repaired. I haven't checked the voltage in yet but will do, the fuse is good, ive checked it. I have to get a proper socket or wrench to fit the flywheel nut to take it off to check the anti-reverse spring and distributer. I'm getting a spark tester tomorrow. Will let ya'll know this weekend.

 

[57 7.5]

Well it was the pulse pack, I checked the power out and got nothing. When I took the old one off it was all gooey and melted underneath. Replaced it and it fires right up now. Thanks for all the help.

 

[Topkill]

57 7.5, Did your issue stay solved after you replaced the pulse pack?

I just bought a 1972 Johnson 100 from a friend that is really clean, but as I mounted it to my pontoon I noticed a gooey substance coming from behind the pulse pack. I have not yet tried to start the motor, but his mechanic just gave it a clean bill of health. What I am thinking is that maybe he just didn't notice the epoxy melt from behind the pulse pack while he was running.

I guess one question I have for the group is what things could cause the pulse pack to melt down? I assume it could be something inside the power pack, or a ground that is not connected, but is there some other failed electrical component that would cause this? I am okay with getting a new pulse pack, but I don't want it to happen to that one too. I have shown a picture below the goo oozing out and of the back of the pulse pack after I uninstalled it from the base plate.

Also, before I got the motor in my possession, 2 things happened that I am wondering if they could have caused the issue. First, my friend had it in the back of his truck with the cowl off, and it poured down raining on it for 4 or 5 hours (the day before I got it last week). Then, he put a tarp over it in case it rained again, but instead it was just blistering hot outside the next day. Could the rain or the greenhouse effect of the tarp have caused the epoxy in the back of the pulse pack to melt and ooze out? If so, could I just re-epoxy it and go on about my way? Before all of this, the engine did sit for a long time without being used. I don't think it has been used a lot in it's long lifetime. The paint is still really fresh on most of it, and the engine is not dirty at all.

 

[F_R]

If it is melting/running out/goo/whatever, it is no good. Frankly, I've never seen one do that. But it has been years since I've seen any at all. It may be an aftermarket unit too. I dunno.

As for what makes them fail, they are extremely sensitive to voltage spikes. The most common cause of those are bad connections, especially in the battery/charging system, but not strictly limited to that. Disconnecting a battery while running is just asking for it. Many fail for no identifiable reason. I was so glad when the Mag CD system replaced it.