78 johnson 140 stator causing issues?

[yankee boy]

I have a '78 Johnson 140 and am having problems starting and idling after running for about twenty minutes. It seems like I am not getting any spark but I haven't been able to check it when the problem is occuring. The problem seems to be repeatable. I have rebuilt the carbs, replaced the gas lines/fuel filter/water separator, coils and plug wires. I did some basic troubleshooting from a clymer manual and when I ohmed out the stator I got 302 ohms on both sides. The manual said it should be be 485-635 and to replace it if it is out of that range. Would this be causing the problem I am experiencing when the motor warms up?

History: The problem started at the end of last summer and I chalked it up to the spark plugs which were two summers old. I let the boat sit at the dock overnight and put in new plugs in the morning. The boat ran fine back to the ramp, only ran for about twenty minutes. I went for Oysters mid December and she ran good for the two hour adventure, the weather was in the low 50's. Upon taking her out the first time this year, she ran great for what I am guessing was the first twenty minutes and upon slowing down for a no wake zone she started getting rough so I had to keep her around 2000 rpms to keep from stalling. Once I reached the dock, she stalled and I was unable to start her. I waited about five minutes and was able to get her going with a fast idle but was unable to get her in gear without stalling. I have only gone out twice this year but it has happened both times. When I get back to the house to flush 30 minutes later, the idle is rough and I need to idle around 2000 rpms to keep from stalling. The following day she will crank right up each time.

Thanks for any advice in advance.

 

[tashasdaddy]

Re: 78 johnson 140 stator causing issues?

1st if you are going to work on it yourself, burn the Clymer. get the Johnson OEM service manual. http://www.outboardbooks.com/

have you check compression and spark on 4 cylinders? did you check spark when it would not start. it could be a coil, power pack, stator, pickup sensor heating up and failing. can you see any cracks in the stator coils, or an oooosseee that has dripped off the coils, on to the top of the motor.

i have the same motor.

 

[yankee boy]

Re: 78 johnson 140 stator causing issues?

I haven't checked the compression when I am having issues. I checked in the drive the other day and the spark was good and the compression was 100 100 110 and 105. The compression was the same when I received the boat a few years ago. Since it hasn't changed I didn't think it would be the culprit. Cold starting has always been good. I replaced all four coils a couple weeks ago because two of them were original and I couldn't change the plug wire. I will take a closer look at the stator coils. It was starting to rain when I checked the stator the other day so I took the resistance reading and quite because the clymer manual said it needed to be replaced.

I guess I really need to check for a spark when the motor is experiencing issues but I don't want to get stranded.

I do need to get the oem manual but I was hoping for verification on the resistance test.

 

[wilde1j]

Re: 78 johnson 140 stator causing issues?

You might try the CDI/Rapair website. They have a free *.pdf download for trouble shooting ignition systems, which may provide other tests you could do.

 

[emdsapmgr]

Re: 78 johnson 140 stator causing issues?

Check the spark on the engine when it is missing. An inductive timing light will show if any of the plug wires are misfiring or not firing at all. If the problem is on one side of the engine only, swap the power packs and see if the problem transfers to the other side.

 

[tashasdaddy]

Re: 78 johnson 140 stator causing issues?

excellant advice.

 

[yankee boy]

Re: 78 johnson 140 stator causing issues?

I know enough about outboard engines to swap the power packs and do basic troubleshooting, but I don't want to get out on the water and have the possibility of getting stranded. The reason I was posting here was to find out what problems will result from a low resistance value. The 300 ohms that I am seeing is way out of spec and I wanted to know if anyone knew enough about stators to know if this would be causing the problem or if it is nothing to be concerned about. I plan on pulling the flywheel tomorrow to get a better look at things.

 

[emdsapmgr]

Re: 78 johnson 140 stator causing issues?

I'd check the stator output voltage before condemning it. Should put out 150 volts at cranking rpm, 250 when running. You'll need a peak reading voltmeter.