Spark Plug Maintenance on Yamaha 2 Strokes

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Raptor1472

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Hi All,

Last season I was doing some maintenance on my 1995 Yamaha 200TXRT 2 strokes, including doing some spark plug replacements.

I bought the SELOC Yamaha Outboard 1984-96 Repair Manual for reference, and in the spark plug section, upon installation of the new spark plugs, it says to use a torque wrench to tighten to 14ft/lbs, which I did.

Not long after, I had a mechanic come out to diagnose a separate issue, and upon removing my spark plugs he said they'd been overtightened and squashed the seal rings. I told him I was following the spec in the manual, and he said he'd never heard of a torque spec on a spark plug, and to always just tighten 1/4 - 1/2 turn past snug.

Is the advice from the mechanic accurate to your experience, or should I be following the torque spec - and if so, if it was indeed overtightened, may I just have an inaccurate spark plug torque wrench? (very possible, since it wasn't an expensive set).

Thanks!
 
I believe i had the same outboards, 98 twin 150 HP Yamahas with carburators on my BW 23 Outrage.
They continuously fouled the plugs when trolling for a longer period so i got used to pull and clean them, also off-shore...
I always tighten them from hand tight another 1/4 turn, same on cars and that is what i always did without having problems. Some state that spark plugs without seal rings 1/4 turn and the ones with seal ring 1/2 turn, however i think 1/2 is excessive.
14 ft/lbs = 19 newton meter what is about right for head thickness of 12mm, at least on cars.

When the non oem Manual say 14ft/lbs the i would believe that as it makes sense on a outboard aluminum cylinder head. You may check for a original Yamaha User Manual (i don't have mine anymore, but you may check online) to see if same torque is mentioned there just to verify this.

Not sure what mechanic wanted to say with squashed seal rings, did he showed you the squashed one/s?
The relatively soft aluminum seal rings have to be "squashed" to seal correctly so it would be interestimg what exactly he mean with that statement.

What i had happen is that a brand new torque wrench was considerable out of spec and seller replaced it so you may check if your torque wrench is working correct.

Chris
 
I would never trust an aftermarket manual for torque specs - although that 14 ft/lbs sounds about right from memory. I say "from memory" because I have never ever torqued a spark plug. Always by "feel".

There's no issues if you tightened it too much. It's just not advisable. Obviously there's an exception to this and that's tightening it so far that you strip the threads.

Torque wrenches need to be calibrated if you're going to use them.
 
I think your mechanic needs to read the manual:)
There is a difference between installing a new plug as opposed to reusing a plug. In the first case the washer does need to be crushed.
The Yamaha manual states that the plugs should be hand tightened and then tightened 1/4 to 1/2 turn. The 1/2 turn is probably appropriate for new plugs. I guess it is easier to overtightem reused plugs since you don't feel the washer compressing. Yamaha also recommends using an anti-seize compound on the plug threads. That is important to keep in mind as using a compound does affect the required torque. That said, over time you will get the feel for when a plug is tightened correctly both when new and when reused. Next time you pull the plugs it may be obvious if they were over over tightened. The spec for the 150 SX model calls for 18 ft lbs and in my younger days, I would use a torque wrench. That teaches you how a properly installed plug feels
 
the rings are supposed to squish. I never use a torque wrench on plugs...1/4 to 1/2 turn past tight is what everybody does.
Like seasick said, with the new vs reinstall...

If you don't get your torque wrench calibrated evry year and after evrytime you drop it, it is really just wishfull thinking anyways.
I admit, I have a set of Harbor Freight torque wrenches just to make me feel better,,,but I have no idea how accurate they are.
 
Thanks for the feedback, everyone! Much appreciated.

To confirm, they were new plugs at 14 ft/lbs, but it seems like the consensus is 1/4 - 1/2 turn, so when I swap all plugs before the new season I'll follow this advice.

Anyone know where to get an OEM manual? I honestly didn't realize Seloc was a AM brand, just figured it was part of Yamaha nomenclature.
 
I find the Seloc manuals to be decent and in some cases more detailed than the OEM manual.
It probably not realistic to expect to find a 'new' 1998 service manual. That said, I may have an electronic version of the manual. If I find it, I will private message you to get your email address.
 
I do have an electronic copy of the Yamaha generic service manual for SX motors including your 200. The file is about 10 Mb and may or may not be emailable. It depends on your email sizing limits.
Send me your email either on this forum ( everybody will know it!) or PM me with it.
 
The next time you are installing new plugs note what the torque reading is at 1/4 turn after snug. 1/4 turn past snug has served me well for ~50 years without breaking out a torque wrench (I own three!).
 
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