Yamaha F115 Spark Plug Color

gregdan24

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Feb 16, 2009
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Hello all. I am looking at a Sea Pro SV1900 with a F115. The owner says he didn't like how light one of the plugs looked so he pulled the fuel rail and injectors and had the injectors ultrasonically cleaned.

Today we did a compression test on it - 170 to 175 psi in all cylinders, so that seemed good. One thing I noticed though was the bottom plug's porcelain was a light tan color but the top three plugs were all pretty much white. I'm sure that the only run time lately and since the injector cleaning has been at idle on muffs.

Hoping to take it out for a ride this week. Taking another look after a good run may tell more. I know it's harder to get color on a plug with pump gas these days and that lean is mean, but wonder if this is normal or something to be concerned about.

Thanks in advance. -Greg
 

Silvertip

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Sep 22, 2003
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28,758
Re: Yamaha F115 Spark Plug Color

Ever watch a NASCAR practice? If you did you will notice that when they are setting up the carburetion (fuel injection actually) they make a couple laps at wide open throttle as much as they can. When they decide to come in they kill the engine immediately and coast to the pits. That's when you get an accurate reading of plugs. Idling will not yield anything of value -- especially if it is just a short run time..
 

gregdan24

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Feb 16, 2009
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Re: Yamaha F115 Spark Plug Color

Ever watch a NASCAR practice? If you did you will notice that when they are setting up the carburetion (fuel injection actually) they make a couple laps at wide open throttle as much as they can. When they decide to come in they kill the engine immediately and coast to the pits. That's when you get an accurate reading of plugs. Idling will not yield anything of value -- especially if it is just a short run time..

Never watched NASCAR practice, but I have heard this before, so you are right for sure. Gonna be tough to go WOT and coast into the launch down here at Pine Island! I did think it was odd though that the bottom one was the only one that showed tan. Maybe gravity has something to do with what's going on in the fuel rail at idle....who knows.

I was sorta wondering if someone would come in and say that the plugs on their F115 or other 4 stroke looked white most of the time or if they always have the normal tan color to them.
 

99yam40

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Sep 7, 2008
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8,851
Re: Yamaha F115 Spark Plug Color

pressurized rail should not be affected by gravity.
just need to make sure pressure is staying in spec at all RPM
 

gregdan24

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Joined
Feb 16, 2009
Messages
29
Re: Yamaha F115 Spark Plug Color

pressurized rail should not be affected by gravity.
just need to make sure pressure is staying in spec at all RPM

Thanks for confirming. Hopefully after running it good they will look ok. Gotta get a manual for the F115 now - I like working on my own stuff as much as possible.
 
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