Spark plug question

[tphoyt]

Good day all
I have picked up a 1985 30hp Johnson
J30elcoa and it’s a 100/1 mix
I’m not crazy about running that so I’m going with 50-1 but the plugs are fouling and it just doesn’t run as smooth with this mix.
Does anyone have a suggestion on using a hotter plug?
thanks for your help
Tim

 

[jakedaawg]

Plugs likely are not failing due to 50:1. Its not the oil that fouls them really.

Check compression 1st. Check spark on an open air gap spark tester step to 7/16" you want a really strong crisp blue snap.

if those are all good look to mixture. Joe Reeves has a good write up on tuning. Make sure all is right before going to a non standard plug in my opinion. However, I dont do many of those old 30's so I am sure there will be better advice coming along.

 

[racerone]

50:1 does not foul plugs.----Just another tall tale that won't go away.------Check thermostat.----Post compression values.------Cold / cooler combustion temperatures may foul the plugs.-----Electric primer leaking perhaps ?

 

[F_R]

100:1 was a serious mistake. OMC came out with a service bulletin saying to run 50:1 and destroy/remove the 100:1 decal. Use UL77JC4 plugs and don't expect them to run "clean" if you do a lot of slow speed running. You ought to see the ones that have been in my motor for at least 15 years. They look so crappy that they shouldn't run by the old school of thought. But they do, and never miss a beat.

 

[Vic.S]

Good day all
I have picked up a 1985 30hp Johnson
J30elcoa and it’s a 100/1 mix
I’m not crazy about running that so I’m going with 50-1 but the plugs are fouling and it just doesn’t run as smooth with this mix.
Does anyone have a suggestion on using a hotter plug?
thanks for your help
Tim

As pointed out 50:1 is now the recommended fuel mix.

It might be worth carrying out a compression test as suggested to find out if the 100:1 mix has caused any problems in that respect.

The recommended plugs are now QL77JC4, gapped at 0.030" ( QL77J4 or L77J4, gapped at 0.040", would have been supplied originally ) Alternatively QL82C are suitable.
Surface gapped L78V can also be used but only for sustained high speed operation..

You dont say what plugs you are using at present.

 

[F_R]

100:1 was a serious mistake. OMC came out with a service bulletin saying to run 50:1 and destroy/remove the 100:1 decal. Use UL77JC4 plugs and don't expect them to run "clean" if you do a lot of slow speed running. You ought to see the ones that have been in my motor for at least 15 years. They look so crappy that they shouldn't run by the old school of thought. But they do, and never miss a beat.

Oops, slip of the brain there. I meant QL, not UL. My bad.

 

[tphoyt]

Thanks for all the input
to answer some questions
The compression is 120 and 125
my gauge leaks a bit so it’s a bit better than that.
The currant plugs are NGK B7HS10
gapped at 0.030”
The electric primer has been removed and replaced with the pull style primer.
So I will try the QL77JC4 and see if that helps
thanks again for the tips
Tim

 

[racerone]

The electric primer is a QUALITY item.----Very reliable.----Works like magic.-----Why was it removed ?

 

[kbait]

The NGK’s were definitely wrong.. NGK BZ7HS-10 would be equivalent to the champions. I’d go with the champions and be sure you’re dialed in on the low speed mixture setting.

 

[tphoyt]

Thanks again for the reply’s.
Im not sure why the electric choke was removed.
It was this way when I got it. The mount on the carb is there so I know it was there at one time. Someone took the drain plug out of the bowel and put a barbed fitting in to hook up the manual choke.
I got rained out this afternoon so I’ll swap the plugs out tomorrow and keep you all posted.

Take Care
Tim

 

[oldboat1]

Don't confuse chokes and primers -- different animals. I believe some of the '85s had primers, others chokes.

I would block off the drain plug fitting and see if running improves. In addition, try adjusting the mixture needle (close slightly first -- leans mix). Adjust while running in a test barrel or in the lake -- water should be about half way up the leg.

 

[Vic.S]

The NGK’s were definitely wrong.. NGK BZ7HS-10 would be equivalent to the champions. I’d go with the champions and be sure you’re dialed in on the low speed mixture setting.

I' afraid I have to disagree with you there.

B7HS-10 or B7HS ( the -10 indicates that they are supplied gapped at 1.0mm) will be suitable, They are merely unsuppressed versions of BZ7HS-10.and equivalents of L77JC4 which would also be suitable, being the modern replacements for L77J4
Z in the number indicates, like Q in a Champion number. that they are inductively suppressed

What are incorrect, and will cause problems, are resistor suppressed plugs such as NGK BR7HS-10. Unfortunately these are often listed and sold as equivalents to QL77JC4 and are probably the cause of the myth that NGK plugs are unsuitable for Johnson and Evinrude engines.

Not relevant in this case but Champion "Q" (or NGK "Z") plugs should be used with VRO or OMS equipped engines.

 

[tphoyt]

Great bit of info.
I love how much you can learn from this site.
I often just sgin in to read through the post to pass some time.
I know a couple guys that swear by NGK plugs and will only use them.
Its starting to sound like it may not help to swap out the plugs but I’ll give it a shot anyway just Incase.
You are correct about the choke that was my fault I should have used the correct term. It did have and electric primer at some point the mount is on the carb and the wiring is still in place.
Anyway I’ll get back on this after work today and let you know what happens.
Enjoy the day.
Tim

 

[tphoyt]

Well not much has changed.
She runs a little smother.
I have to keep in mind this is an old 2 stroke.
I think it need to put her on a skiff and she how she’s runs in the water. It’s just sitting on a stand in a barrel at the moment.
Thanks again for everyone’s input.
If there are a major changes in the near future I’ll post em.
Tim