1993 Evinrude Spark Plug Gap

dnyelator

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Jul 23, 2015
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The online charts say to gap at 0.03 for my 120 HP, V4. Is that right? If I'm reading correctly that is 0.75mm, which is very tight. The plugs I pulled out were at 0.4 or 0.5. Please help!

​Thanks
 

Vic.S

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May 4, 2004
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4,690
The online charts say to gap at 0.03 for my 120 HP, V4. Is that right? If I'm reading correctly that is 0.75mm, which is very tight. The plugs I pulled out were at 0.4 or 0.5. Please help!

​Thanks
Generally the recommended plug gps for most (all??) of the 2 strokes were revised from 0.040" to 0.030" in the late 1980s (??)

I would have thought that your 1913 owners manual would have said .030"..Does it not ?
My 1984 owners manual says 0.040" but the latest recommendation is 0.030"
 

dnyelator

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Jul 23, 2015
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Generally the recommended plug gps for most (all??) of the 2 strokes were revised from 0.040" to 0.030" in the late 1980s (??)

I would have thought that your 1913 owners manual would have said .030"..Does it not ?
My 1984 owners manual says 0.040" but the latest recommendation is 0.030"

​Thanks Vic, I admit I didn't look in the manual, looked it up online, its just that the existing plugs that came out of it are gapped way larger, like I said 0.50, the plugs I bought are also gapped at like 0.40 and 0.50 vs. 0.03. My feeler gauge is in mm, when I crossed 0.03 to mm, I came up with 0.75mm, which is very small. When I bent the prong it just looked so tight I was really surprised, but I'll go with that and swap them out and see how she runs. Thanks for the reply.
 

interalian

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Jul 23, 2009
Messages
2,105
Gaps wear open pretty fast on these motors. I set mine new to 30 thou and they were worn to 40 by the end of season.
 

dnyelator

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Jul 23, 2015
Messages
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Gaps wear open pretty fast on these motors. I set mine new to 30 thou and they were worn to 40 by the end of season.

​You say 30, but don't you really mean .030? That's where I was getting confused. My round feeler gauge only goes down to 30, but that is a lot more than .030. I gapped them at 0.75mm and put them in and it seems be running OK. It's never ran great, but it runs, so I guess that's where they need to be. Thanks for the assistance folks!
 

interalian

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Jul 23, 2009
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30 thou is mechanic's, engineer's and draftsman's shorthand for thirty one-thousandths of an inch. It equals 0.762mm.
 

dnyelator

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Jul 23, 2015
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30 thou is mechanic's, engineer's and draftsman's shorthand for thirty one-thousandths of an inch. It equals 0.762mm.

Thank you sir. Now I know. I misunderstood your "thou" to be "though" vs. "thousands". Should have known. My bad. So I set them to 0.75mm...thanks!
 

interalian

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Jul 23, 2009
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Sometimes I need to remember my jargon may not match everybody's interpretation. A good reminder for me to be more precise. Another example would be 'mil' which old timers use in place of 'thou' as well - that one mixes up people with a passing familliarity with the Metric system.
 
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