Help!,1975 johnson stinger arching around spark plugs

[adam1psu]

i bought this engine used from a very trusted local outboard shop. it ran fine for a while, recently it started missing, as a result the engine would not plane the boat out. after investigating the problem i found that the middle cylinder is only fireing at five to ten second intervals at a time causing the boat to continuously learch forward as it was missing. i ran the engine in my garage with the lights out and found that the middle cylinder plug is arching around the head where it threads into the engine. i never heard of this before. Since i am very mechanically inclined when it comes to cars and motorcycles this was something new. well i replaced the plug, the spark plug wire and then the entire pack for the middle cylinder. It is stil arching. i then thought perhaps the coil pack is not grounded properly so i grounded it to the block using a 10 gauge wire. it still archs. I am at my wits end. I thought it was fixed,:^ then during a major striper tourmanent it started acting up again. anybody have any ideas whats going on here??? I guess thats what i get for running a 1975 engine. ohh and one more thing the engine runs fine leaving the dock to my first fishing spot but when started again it misses due to arching im assumeing moisture is acting like a conducter and making it arch. any help is much appreciated!

[ezeke]

Are you using automobile plug wires?

[adam1psu]

when i replaced the wire on the coil, yes. but now i have a new coil and wire provided with the coil is a marine wire. what is the difference? i would like to know-thanks adam

unless the wires were allready automotive on the other coils. the coils themselves look very old but the wires look new so maybe the other two are automotive:$

[ezeke]

The main thing is that the wires are not carbon core.

Any chance there's a Heli Coil in that hole?

[adam1psu]

possibly, i will look, anything is possible with a used engine. any of you other outboard veterans have any suggestions?? without me telling you about allready replacing everything what suggestions would first come to mind, perhaps i need to recheck all of the ignition wireing.

[fireman57]

If it is known marine wire that came with the marine coil you almost have to have a bad plug. Is the ceramic cracked anywhere? If you swap it with another plug from another cylinder does it still arc? I know that you said you replaced the plug but you didn't say if it was used or even if it was the right plug for your engine. Are you using Champions?

[rwash91]

Adam:
I recently replaced my coils with brand new omc coils and wires and 2 out of four were jumping around the plug to fire to ground. Got 4 new boots at napa for marine engines and that took care of it. Make sure there is no grease or film on the plugs also. The boots I got from napa are super tight to get on and off. Good luck !

[Scaaty]

Try wrapping a wire around the plug body (wrench part), tape it on, and run it to a ground. You might have a Heli-coil or insert in there that was slathered in something, prventing a good ground. If it goes away with a ground wire, thats the proplem

[adam1psu]

well it dosent have have a helicoil in the hole, i do run champions and the right plugs when i got it it had ngk equivilents. the plugs i switched out are new. i will try the ground trick to see bc it seems there is a lot of oil/fuel residue built up on the threads. i will also try new marine plug boots as suggested.

just want to say thanks!- for all the help so far you guys have given me, some were suggestions i would have never thought of

[R.Johnson]

With the engine running, touch a ground wire to each spark plug boot, and see if this will ground out the plug. I have run into this with after market marine boot's

[adam1psu]

another good suggestion, thanks! i will try it in the garage tonight when its totally dark so i can see whats going on. if it works i will try it on the water sat morning.

[R.Johnson]

Running an engine in the dark is not really a very good test. There is a high electrical field around those wire's, and you can see spark's danceing all over. If you could see a solid blue spark, and hear a snap, that would have some meaning, otherwise not.You are seeing what is more like static electricity, and this is normal.

[adam1psu]

well in that case perhaps what i am interpreting as arching might just be static electricity. i now think the other coils need replaced.

[Scaaty]

You should have seen my old Merc XS 150 when I (usually-love that carb sound at WOT!)) had the middle cowling off. Those 6 wires running along the block put on a real light show at night.....

[adam1psu]

i guy i know told me it might be my power pack. nor being a outboard mechanic i dont know what a power packs exact function is. is this a possibility? now i dont even think the plug was arching in the first place. i think i was just seeing static electricity. any suggestions? thanks

[adam1psu]

i am assumeing that it acts like a distributer?

[fireman57]

Do a spark check on all cylinders and repost. you can use a cheapo spark checker from Autopartsforless place in your town. Make sure that the spark is not yellow. Should be bright blue even in the sunshine.

[adam1psu]

will do, thanks

[adam1psu]

well i bought a spark plug tester and none of the coils even remotely showed any sign of spark. i am sure the tester was grounded well and unless the tester is faulty. i am assumeing that whatever is going on that none of the coils have enough power to jump the gap on the testor with a healthy or even weak spark. this includes the brand new coil. the strange thing is that the engine will easily start. from this i gather that the plugs have a weak spark. so any suggestions of what to do next?- thanks adam

[i386]

Is the gap on the tester adjustable? If so, decreasing the gap may let you see the arc. I don't know how far the spark should jump for your engine but someone here will.

[adam1psu]

there is no adjustment on the testor but from what i am told there should be a bright blue spark seen even in the daylight

[adam1psu]

PROBLEM SOLVED! I re-thought everything and went over the engine once more.i noticed a black spot where it looked burnt on the block. there was a loose ground there and now it runs great after tightening the loose wire.

[ezeke]

I am very happy that you posted the solution and that you worked it out.

I think that a lot of money is wasted because people don't take the time to check and to clean the wiring.

[fireman57]

adam, glad you found it and posted your solution too. Just got back from out of town and your's was the first thread I opened. always like to see good news.

[adam1psu]

thanks for the help, i agree, logical deduction can solve a lot of problems if one has knowledge and patience. i am far from a marine mechanic and have allready learned a lot from you guys by just asking questions or reading. unfortunately my problems continue on another thread:'(