74 Johnson surges real bad

[huntxtrm]

My 1974 70hp Johnson surges real bad. It runs about 20, then it's like someone kicked it in the tail. Then on its face again.????

 

[fireman57]

Re: 74 Johnson surges real bad

fuel or spark problem. Clean/rebuild the carbs and make sure there is no junk in them. there could be a speck of something that is shutting fuel off in one of the carbs. You also might have a bad coil. Remove the grounds and clean them good. Look for cracks in the coil or soft spots from heat.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Carbs are spotless, coils have cracks. Someone siliconed the cracks. I'm gonna fire it up in the dark, and see if there is a light show.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Just an update. No lightning show. No visible stray voltage. Gonna put a timing lite on it snd see if it blinks consistent on each cylinder, in the morning.

 

[boobie]

Re: 74 Johnson surges real bad

Do a cyl drop test on it when it's acting up. You may have a cyl or two that is not firing.

 

[huntxtrm]

Re: 74 Johnson surges real bad

I could, but it my be hard to tell. The miss is spuratic. I figure its a coil, It's just not missing every power stroke on that cylinder.

 

[fireman57]

Re: 74 Johnson surges real bad

take a buddy out with you the next time with the timing light. When it starts it again have him watch the light. Make sure you stop before he tries to change the wires to another plug. Sounds like it's about time to replace coils if they are original.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Ok, Took a buddy out with me. Fuel filter is running out of fuel? He thinks its the fuel pump. Any idea on the part number for the kit? or do you have to buy the whole pump? Cant seem to find just the kit? New coils already on order, figured might as well.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Parts headed this way. Lets see which one fixes the problem? LOL

 

[fireman57]

Re: 74 Johnson surges real bad

to test the fuel when it surges have a buddy pump the primer bulb like a madman and see if the engine picks up. If it does just replace the pump. they are fairly cheap. You can also get a rebuild kit and it's simple but the new pumps aren't that much more and you know that it should be right.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Replaced the coils and the pump. I'm gonna take it to the lake today, wind permitting, and try it out. I did have my dad pump the bulb while running across the lake last time. It seemed to help. I installed the CEO coils. Kind of a pain, hope they work.

 

[fireman57]

Re: 74 Johnson surges real bad

Hope it worked and you took a timing light with you just in case.

 

[huntxtrm]

Re: 74 Johnson surges real bad

Installed the coils, installed a new ignition switch. Decided I had better run it on muffs before I took it to the lake. Glad I tried. No fire! I have something haywire, I guess. I hooked everything back up exactly like it came apart. Checked M to M at the switch. No continuity when key is on, cont when key is off. But no fire at the coil wire. I put a spark gap tester on, and now spark. Here is a pic of the rigged up coil install. They are not direct replacements, apparently. Anybody have a motor wiring diagram for a 74 Johnson 70 hp? My book has some of it, but not the harness. Thinking about redoing the harness anyway. The wires are old and brittle.

 

[huntxtrm]

Re: 74 Johnson surges real bad

found the diagram, sort of. figured out the rest. Rectifier was bad. still have a small miss. Gonna sort that out. Watch for a new thread, if I cant figure it out.. Thanks