What would you do? (spark plug question)

[JerEazy2]

S150TXRU

So, the service manual says between .035 and .039 - and the little plate inside the cowling says .040 for the gap.

I know at the end of the day, it isn't a HUGE difference. But, i did at .040 before i got the manual, and i do have a bit of a "wobbly" idle that MAY be caused by a bit too much of a spark plug gap (and my timing is probably off a bit because i twisted an incorrect screw this one time.... But that's a different story)

Would you follow the manual? Or follow the sticker? Or would you even care? haha

[boscoe99]

Try gapping it at the minimum of 0.9 mm and see if it gets better or worse.

The preponderance of Yamaha data indicates 0.9 ~ 1.0 mm. I find nothing that indicates 0.040".

[robert graham]

Run it about .036 of an inch and then if you experience some erosion or wear on the center electrode you'll still be within specification.....no need to start at .040

[JerEazy2]

Try gapping it at the minimum of 0.9 mm and see if it gets better or worse.

The preponderance of Yamaha data indicates 0.9 ~ 1.0 mm. I find nothing that indicates 0.040".

sorry Boscoe - I was talking inches.

[JerEazy2]

As the plug wears, the gap gets BIGGER..

I'd personally go .035" or .036" . As it wears, it stays inside spec's..

Kinda where my head was at too.

Thanks.

[rodbolt17]

whuuuut?
that sheet will spark and run perfect anywhere between .025" and .055". .039 is what it had originally.
you do realize it is simply not that critical. the cap resistance is.
instead of dinking with plug gap fix your running issue.

[JerEazy2]

whuuuut?
that sheet will spark and run perfect anywhere between .025" and .055". .039 is what it had originally.
you do realize it is simply not that critical. the cap resistance is.
instead of dinking with plug gap fix your running issue.

wuz just a curiosity Mr. Bolt.

Borrowing a friends timing light and will get the timing set properly next time i can get to the boat.