Question about replacing Yamaha Spark Plugs

[boscoe99]

This thread makes it easy to see why the FAA mandates that mechanics follow maintenance procedures under penalty of law.

[panasonic]

My 2 cents. There was a time when changing spark plugs was much more frequent...they just didnt last. Now with modern engines plugs can be in for many years without the need for changing or cleaning. So when it's time to change them they might very well be corroded and difficult to remove.
A little dab of antisieze on the threads can be all the difference between a quick painless plug change or a nightmare of broken plugs and stripped out threads.
After saying all that I have repaired many a spark plugs holes with helicoils but would say that corrosion was not the problem in most cases...but being over torqued and/or cross threaded was the cause.

[panasonic]

This thread makes it easy to see why the FAA mandates that mechanics follow maintenance procedures under penalty of law.

We use antisieze on the ignitor plugs of our jet engines, but they are not in long enough for corrosion to really be a problem...they consume themselves fairly quickly.

As for the piston engine planes I believe they use a dry graphite product on the plug threads. I really can't remember as it's been a long, long time since I changed plugs on one of those...

[boscoe99]

We use antisieze on the ignitor plugs of our jet engines, but they are not in long enough for corrosion to really be a problem...they consume themselves fairly quickly.

As for the piston engine planes I believe they use a dry graphite product on the plug threads. I really can't remember as it's been a long, long time since I changed plugs on one of those...

In the US mechanics don't have a choice. They have to use what the maintenance manual says to use. If nothing is specified, then nothing gets applied to the threads of the plug.

Folks have been hurt or died due to mechanics thinking they know better and then doing stuff their own ways.

Having said that, back at the factory the engineers argue over what should be used and when. Just like is argued here.

[zenoahphobic]

In the US mechanics don't have a choice. They have to use what the maintenance manual says to use. If nothing is specified, then nothing gets applied to the threads of the plug.

Folks have been hurt or died due to mechanics thinking they know better and then doing stuff their own ways.

Having said that, back at the factory the engineers argue over what should be used and when. Just like is argued here.

If everything is Mandated then an argument can be made: what are mechanics? and why are they then needed if they have no discretion.
It needs to be said this spark plug issue is hardly where people may get hurt or die, or that anything at all will happen whether the thread is lubricated!

[99yam40]

I am fairly certain that he was meaning that on airplanes, mechanics cannot just do what they want to.
if some people die due to what they did and they did not follow procedures set in place, they will be liable.

maybe if a tech does something that is not the correct thing listed to be done on another vehicle that causes death or other problems, they will also be in trouble.
kind of reminds me of no one wanting to turn rotors or drums anymore in case they fail in some way.

in my lifetime I have found out there are good mechanics/techs and there are bad ones too.

some that are just part changers that hope they can fix things

spark plugs may not kill people, but they can cost you a lot more if the threads are pulled and heads need to be repaired or heads replaced

[Keithbaja]

A thread chaser is not a tap or cutting tool. Its used to clean the threads
can be used on slightly bad thread on aluminum. TIP if U can't get started with UR fingers put a piece of fuel line over the procain and twist. TIP 2 If U ever drop a plug not in the box, Throw it away and get a new one. Install with no oil or antizeeze. Its fine to take plug wire and turn upside down with a shot of a good oil for corrosion protection. Your hear a lot of wanna bees boat techs say there are no marine spark plugs for I/Os or inboards. B.S. !! AC delco non automotive spark plugs. Look it up. Great NGK note from Townsend. I don't use RTV, electrical Tape, Antizeeze. Nuts and bolts go back together with OMC Triple guard. Happy New Year to All.

[robert graham]

My 1999 C-90 Yamaha still has the original spark plugs….I just remove them, sand-blast carbon off until clean, a drop of oil on threads, check gap,back in motor…I have a new set of plugs in my tool box if I ever need them. We average using the motor about 21 to 28 days per year, use Lucas 100% Synthetic oil in premix,Ringfree and Stabil…..Plugs never seen to actually wear, just very light carbon. I don’t think plugs on outboard motors wear out much….

[byron.akhavi@gmail.com]

Thanks for the responses. I contacted Yamaha and NGK. They advise to remove and replace with new plugs (don't install old plugs).

Thread hand tight and then apply torque slowly to attain 13 lbs.-ft. No lubricant or anti seize. Just new, clean and gapped plugs.

They recommend threading in and ensuring a smooth forward and reverse movement (thread anti clockwise until the threads "click" into place). Then apply torque until spec. The crush washer takes time to set and it will seem that torque is constantly being applied for a while. However, the spec. will be reached and the plug will be installed correctly.

They also suggested changing yearly to avoid stuck plugs that are difficult to replace. It seems NGK applies a treatment to the plug threads. This is what Yamaha and NGK suggested. You guys have great suggestions and I plan to remove, install by hand and just torque to spec. Do not agree with yearly changes....but checking the plug condition has its advantages. Thanks again for the assistance.