Spark Plug Gap

[scatgo]

Looking for information on the right spark plug gap for a 1980 johnson 35 HP. still waiting for the factory manual that seems to be lost in the NJ postal system for a week now. Thanks for any input.

 

[Chris1956]

The are almost all .035"

 

[racerone]

Spark plug gap can be 0.025" to 0.040" and motor will run just fine.------What running issues do you have ?

 

[robert graham]

If you don't have a feeler gage/gapper, then just set the ground electrode perpendicular with the center electrode and you should be pretty near correct....as mentioned, .035" is pretty much normal.....

 

[Vic.S]

Looking for information on the right spark plug gap for a 1980 johnson 35 HP. still waiting for the factory manual that seems to be lost in the NJ postal system for a week now. Thanks for any input.

The currently recommended plugs are Champion QL77JC4 gapped at 0.030"

See http://continuouswave.com/whaler/ref...gChart2008.pdf


When new it would have had L77J4 , which are obsolete, or possibly AC M40FFX

The gap would originally have been 0.040" but gaps were changed across the board to 0.030" in the late 1980s
When your manual arrives you may well find it refers to the old plugs and gap.

My understanding is that the plug gaps were reduced to improve plug life ... You are unlikely to notice any difference it the way it runs

 

[scatgo]

Spark plug gap can be 0.025" to 0.040" and motor will run just fine.------What running issues do you have ?

I put a pair of new NGK plugs in and the boat idled real bad. When I put the old Champion plugs in it ran smooth as glass. My guess at the time was the gap might be wrong on the NGK plugs but not knowing what the gap is i just left the old Champions in for now.

 

[scatgo]

The currently recommended plugs are Champion QL77JC4 gapped at 0.030"

See http://continuouswave.com/whaler/ref...gChart2008.pdf


When new it would have had L77J4 , which are obsolete, or possibly AC M40FFX

The gap would originally have been 0.040" but gaps were changed across the board to 0.030" in the late 1980s
When your manual arrives you may well find it refers to the old plugs and gap.

My understanding is that the plug gaps were reduced to improve plug life ... You are unlikely to notice any difference it the way it runs

Thanks. Great info.

 

[Vic.S]

I put a pair of new NGK plugs in and the boat idled real bad. When I put the old Champion plugs in it ran smooth as glass. My guess at the time was the gap might be wrong on the NGK plugs but not knowing what the gap is i just left the old Champions in for now.

NGK plugs should be ok but be sure you use the correct NGK plugs .Most of the world prefer NGK plugs.

Champion "Q" series plugs are inductively suppressed.

If Champion Q series plugs are recommended DO NOT use resistance suppressed NGK plugs ie those with an "R" in the number. Either use inductively suppressed ones, which have a "Z" in the number or use un-suppressed ones.

For example if the recommended plugs are Champion QL77JC4 you can use use NGK BZ7HS-10 or B7HS-10. but NOT BR7HS-10

The resistor NGK plugs are often listed as equivalent to Champion Q series plugs ........ They are not!

Inductively suppressed plus should be used in engines with VRO or OMS rather than un-suppressed plugs

Incidentally the -10 in the NGK number denotes that they are supplied gapped at 1.0 mm They will therefore need to be re-gapped to between 0.7 and 0.8 mm ( 0.030").

 

[flyingscott]

Champion plugs will.run better in an OMC motor.

 

[scatgo]

Thanks everyone. Great information.

 

[scatgo]

Champion plugs will.run better in an OMC motor.

Can someone please explain OMC? I know Jonson and evinrude are the same thing but OMC is a mystery to me.

 

[racerone]

OMC = Outboard Marine Corporation.------Marketed Johnson / Evinrude from about 1932 to 2001 or so.

 

[oldboat1]

OMC from 1956 (Outboard Marine Corporation). Evinrude dates back to 1907 or '08.

 

[racerone]

In 1936 it was known as ----Outboard motor & manufacturing company.----Selling both Johnson and Evinrude

 

[oldboat1]

Hey -- you need a feeler gauge, Scatgo. Have to say, though, my Champion plugs always seem to come out of the box gapped at .030 -- so have to believe your motor would likely run fine with shiny new plugs right out of the box.

 

[scatgo]

Hey -- you need a feeler gauge, Scatgo. Have to say, though, my Champion plugs always seem to come out of the box gapped at .030 -- so have to believe your motor would likely run fine with shiny new plugs right out of the box.

When it comes to spark plugs i think i have OCD. I have never installed a spark plug with out using a feeler gage. Even if it says what the gap is on the box. LOL Thanks for the information every one.