Johnson 140hp idle/running issues... next step?

[CharlestonMako]

Please help me get my boat back in the water!

THE MOTOR? My 1988 Johnson 140, 4 cylinder, pre-mix gas is having issues. After running great for 2 years, I was out one day and the problems started mid-trip? took it home and have the same issues on the hose.

WHAT IT DOES? It will start alright usually, but typically will run a little rough, and not real even. Kind of a ?BUM! bum bum bum BUM! bum bum bum? kind of sound that is not normal. That will last 5-10 seconds then it will stall. Sometimes I can get give it a little throttle, and get it idling around 1500-2000 RPM and it will stay running, until I try to give it more throttle, or bring it back to idle? then it will stall out again.

WHAT I HAVE TRIED? I have taken it off the internal tank, off the water separator, and put on external tank with fresh gas. I tried running a treatment of seafoam through it. I replaced the plugs. I checked the spark on the plugs by holding them against the block? all are producing small blue sparks. I ?half rebuilt? the carbs? took them apart, and cleaned the jets, but didn?t use a new rebuild kit? they looked very clean, and all jets are clean.

OTHER SYMPTOMS? When I replaced the plugs, I turned it over a couple times then pulled them again. Three were a little wet with dark fuel, but still clean, but one was obviously dirtier than the rest, and after running for only about 20 seconds, was covered in black. Also, when I look into the cylinders, the two top pistons look kind of wet, but not smooth, like black wet 150 grit sandpaper, but the bottom two pistons seem dry with a ?matte? grey/black looking finish? obviously different than the top two?

I?ve done about all I can think of now? could this be a timing issue?

Thank you

 

[CharlestonMako]

Re: Johnson 140hp idle/running issues... next step?

forgot to mention that I also tried an autozone spark tester, but couldnt get any of the cylinders to spark with it... I figured it was the wrong kind or something, because there obviously is a spark of somekind because it runds for a while... plus there are small blue sparks, when the pug is held near the block... does this "ametour" test mean I can eliminate spark issues?

thanks

 

[bustermin]

Re: Johnson 140hp idle/running issues... next step?

forgot to mention that I also tried an autozone spark tester, but couldnt get any of the cylinders to spark with it... I figured it was the wrong kind or something, because there obviously is a spark of somekind because it runds for a while... plus there are small blue sparks, when the pug is held near the block... does this "ametour" test mean I can eliminate spark issues?

thanks

spark should jump 7/16 gap on tester, if its not doing that then you dont have a strong enough spark. also, have you check compression? as far as holding it to the block, that can tell you if you have spark but you should be able to hear a very audible snap from the spark. you could also try pulling the plug wires while its running, if it doesnt change then you know which cylinders are missing.

 

[CharlestonMako]

Re: Johnson 140hp idle/running issues... next step?

I will try and find a better tester... the one from autozone literally fell apart during use.

I did a compression check when I first got it two years ago, and all 4 cylinders where 120 +- 3psi. I havent checked lately though.

If the problem is from cylinders not firing, its got to be two... becuase I have run the boat on three, and it runs fine... the only way I could tell is a loss of top end RPMs... that being said, if the problem is that it is running on two, then I would have at some point been running on only 1 as I was going the spark tests yesterday... will a motor do ANYTHING on one cylinder? with ONE plug out to test, it ran for 5-10 seconds.

could the spark be too small to ignight every cycle, but still show up when held against the block? what could cause this? my plug wires are pretty old.

Thanks

 

[another todd]

Re: Johnson 140hp idle/running issues... next step?

Was the real dark oily plug the lowest one? You may, like me, have a recir. problem. I have two of the 5 check valves stuck, and am awaiting parts. I assume this is a looper similar to my 1995 130.

 

[jonesg]

Re: Johnson 140hp idle/running issues... next step?

I will try and find a better tester... the one from autozone literally fell apart during use.

C'mon...fix it. You need it. I have their tester, its cheap but quite usefull.

could the spark be too small to ignight every cycle, but still show up when held against the block? what could cause this? my plug wires are pretty old.

Compression suppresses the ability of the spark to jump the gap when installed in the head.

I'd say you have poor/dead ignition and lots of unburnt fuel.

Swap the good coils for the bad ones, clean all grounds and connections whilst doing this ,
and look very closely at the bad coils for cracks.
If the problem follows the coils you need new coils.

Also check the shift interrupt switch at the shifter on the side of the block, disconnect it and try again.

If all checks out ok then you need to start doing tests on the power pack or throw money at it.
If you don't have the factory manual you need it.
www.outboardbooks.com

 

[CharlestonMako]

Re: Johnson 140hp idle/running issues... next step?

Thanks for the comments guys...

Was the real dark oily plug the lowest one? You may, like me, have a recir. problem. I have two of the 5 check valves stuck, and am awaiting parts. I assume this is a looper similar to my 1995 130.

Yes, the oily plug was the bottom starboard plug. What is a recir problem, and what are these check valves? yes, a looper

Swap the good coils for the bad ones, clean all grounds and connections whilst doing this ,
and look very closely at the bad coils for cracks.
If the problem follows the coils you need new coils.

How do I know which coils are good and which are bad? does the single oily plug indicate the coil is bad, and its not firing?

I already took the tester back... I'll go buy another one if its important. Can you just clip it to any metal and it should work, even if it is painted?

thanks for all the help...

 

[CharlestonMako]

Re: Johnson 140hp idle/running issues... next step?

OK, I just found this adjustable tester at Advanced Auto... will give thgis a try thise weekend:

http://i1.lelong.com.my/UserImages/Items/0810/21/aaronngu77@12.jpg

 

[CharlestonMako]

Re: Johnson 140hp idle/running issues... next step?

ok... got some more info.

I tested the spark with the adjustable tester. All 4 were sparking, but non were really conistant at 3/8" gap, between the tester's leads, as estimated with a measuring tape.

Three of them would spark loud (could hear it over the motor) blue sparks, off and on at 3/8" but never consistant would stop for a couple seconds, then start back for a couple seconds... back and forth. If I reduced the gap to about 1/4" on those three cylinders it sparked continuously.

The bottom starbord cylinder wasent quite as good... which is the one who's plug occationally looks a little dirtier. It would rarely spark a couple times at 3/8", spark off and on at 1/4" and continuously at a little less... maybe 3/16" or so.

I pulled the bottom strabord coil, and cleaned the connections and checked for cracks... couldnt find any.

now what? I was going to check the other coils today, but is the little less than ideal sparking a problem? I ordered new plug wires... the ones I have are real old looking, and are not conducting all that well (can only get continuity on two, but all are in the 2kohm range...this ok?)

Note that with each of the 4 plug wires off to test spark, it seems to run about the same... will continue to run if you find the right RPM, but bogs out in idle.

Thanks,
-Eric