1975 Johnson 115 V4 quit suddenly

[tjatech]

First post on this forum - Looks like a great place for help.

Anyway, my 1975 Johnson 115 cut out at WOT last week. The motor was running great and then stopped like somebody turned the key off. I haven't been able to get it started since. It turns over just fine, but worn't start.

I first checked the fuel system since it is easiest. It looks like I'm getting fuel to the carb, but when I roll over the engine with the plug out it doesn't seem like I'm getting fuel to the cylinders. Any idea why I wouldn't be getting fuel there?

Also, I was thinking since it stopped so fast it may be an ignition problem. I checked the spark by sticking a screwdriver in the plug wire and holding it by the block. I got about a 3/16" Arc. Does this sound like a strong enough spark?

Any thoughts on this problem helps, I'm stumped right now. Thanks in advance!

 

[emoney]

Re: 1975 Johnson 115 V4 quit suddenly

Could be one of a number of things. Start at the top, you'll thank me later. Compression Test/Spark Test/Fuel System Check. There's several great threads inside the sticky titled, "Top Secret" at the top of this forum, to get you through all three. Where it to be an ignition issue, I would think you' wouldn't be getting spark even at 3/16th. By going through the "Big 3", you can narrow it down to really start troubleshooting. Posts your results here, and someone (or several people) will weigh in with solutions. Good luck.

 

[fishtricker]

Re: 1975 Johnson 115 V4 quit suddenly

how about the primer bulb squeeze and see what happens could be your float is stuck also check the kill switch

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

Thanks for the quick replies. I looked at the "Top Secret" sticky and found some good information. I tested my spark and it looks like it's ok. Compression also looked ok, and all cylinders were similar. The next thing I did was spray some starter fluid in the carb (now realize I shouldn't have used ether). The starter fluid had no effect. Could this mean there is a stuck float? Also, would a stuck float cause a motor to stop instantly at WOT?

 

[wilde1j]

Re: 1975 Johnson 115 V4 quit suddenly

You sure you have spark? Ether should have fired if you did. Check spark (7/16" air gap) again. You should've used premix in a spray bottle, but no harm done.

A sudden failure is usually ignition related.

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

I've got spark on all 4 cylinders, but I'm not sure if it is strong enough. Like I said above, I can get a small arc if I stick a screwdriver in the plug wire and hold it really close (like 3/16") to the block. Does this sound like a strong enough spark or not?

 

[wilde1j]

Re: 1975 Johnson 115 V4 quit suddenly

Get or make an adjustable air gap spark tester. Bought one is < $10 and look like:



Spark should be blue.

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

So after checking my spark with an actual spark tester, it looks like I might be getting too weak of a spark. I was not able to jump anywhere near 7/16". What are common causes of weak spark?

 

[tboltmike]

Re: 1975 Johnson 115 V4 quit suddenly

The primary voltage should be some where around 300 volts. This come from a magnito under the flywheel. This lead goes to the kill switch and then to the ignition. This is what sends power to the Power Pack. I think it is the #1 lead off of the power pack that goes to ignition. Might check out the primary circuit first.

the engine in my avatar should look familiar!

What were your compression numbers? I am doing that to mine now. Getting between 80 and 90 psi.

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

Thanks for the pointers tboltMike. I opened up my powerpack and checked the #1 lead(and all the others) for voltage, and it looks like I'm only getting about 78 volts to the primary circuit. Any ides why it would be so low? Also, is the magneto suppose to create 300 volts, or is there something that steps up the voltage?

Thanks

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

Alright, so I've been doing some more troubleshooting. While checking voltages in the motor, I noticed that the 12 volt device that opens and closes the throttle plates (not sure what its called) is VERY HOT to the touch. Is this normal, or could it be a sign of a short somewhere?

I'm also still troubleshooting my low primary current voltage...any ideas on that?

 

[crb478]

Re: 1975 Johnson 115 V4 quit suddenly

Alright, so I've been doing some more troubleshooting. While checking voltages in the motor, I noticed that the 12 volt device that opens and closes the throttle plates (not sure what its called) is VERY HOT to the touch. Is this normal, or could it be a sign of a short somewhere?

I'm also still troubleshooting my low primary current voltage...any ideas on that?

That is your solenoid and it should not be hot at all. It should only be getting power when you push the key in or flip the switch to choke the motor. See where the power is coming from
that is heating up the solenoid.

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

Alright, so I was as I was trying to figure out why the choke solenoid was so hot, I noticed that if I touch the solenoid ground to the block, I get pretty good sized sparks. I checked the voltage between the solenoid ground and the block and got a solid 12 volts.

Since I new this wasn't good, I disconnected the choke toggle switch from the system (wiring goes through key switch then toggle switch, then to the solenoid), and still got twelve volts between the choke and the block. So then, I just disconnected the entire choke system from the key switch and the voltage between the solenoid and block finally went away.

Does this sound like an issuer with the key switch, or a short somewhere else in the system?

 

[crb478]

Re: 1975 Johnson 115 V4 quit suddenly

Hard to say but I would be leaning toward a short in the wiring. I would start at the key switch to see if any wires are shorting to the choke toggle and then work back from there.

 

[oldrudedude]

Re: 1975 Johnson 115 V4 quit suddenly

You've done some good trouble shooting tjattech. Choking at WOT would certainly cause it to die. If disconnecting the choke toggle didn't deactivate the choke solenoid, it must be shorting down stream from there. Check the terminal block at the engine to ensure nothing is shorting across to the choke solenoid lead. Check for chafe or melted spots in the wiring harness. Tell us what you find.

 

[tjatech]

Re: 1975 Johnson 115 V4 quit suddenly

Thanks for the advice guys. I FINALLY got some time to work on the boat again this week. I looked over the wire harness and checked for obvious shorts, but didn't see any damage. Some of the accessory circuits had some pretty old, beat up wiring, so I ran new wiring for those and cleaned up the terminal connections.

After hooking everything back up, my choke solenoid was still getting really hot and my spark is very weak. I suspect there must be a short at the engine. However, to rule out the harness, I would like to check the voltages coming into the engine. I disconnected the big red connector and tried to check for voltage there, but was coming up with all zero's.

How would I check for voltage at the red connector coming into the engine?