Double Fire Ring on spark plug

[Nezlugh]

I have a 1973 115hp Evinrude, in order to run QL77JC4 I have to put on two fire rings. Otherwise the electrode hits the piston and closes the gap from .040 to .025.

Has anyone ever seen this before? This is a boat that was given to me and I do not have much info on the motor.

Motor runs good WOT on UL77V or equivalent plugs but loads up trolling at low throttle

Thanks for your info!!!

 

[kenmyfam]

Re: Double Fire Ring on spark plug

Are you sure you are using the correct plugs ???

 

[10tori]

Re: Double Fire Ring on spark plug

I have the same outboard with exactly the same problem. I bought it earlier this and got it running last weekend to find that the piston was hitting the plug and closing the gap. I doubled up the washers and it ran good so now I am looking for the correct plugs. Be that surface gap or conventional. Also the plug that was hitting were the ngk's you were using. Keep me updated.

 

[Nezlugh]

Re: Double Fire Ring on spark plug

Yes the ones I first put in the motor were NKG, the plugs I replaced were Autolites with double fire rings. The local part store ordered in the Champion recomended resister plug and before I even installed them we used a micrometer to measure the length and they were the same. I had him send them back.

 

[mmccoy555]

Re: Double Fire Ring on spark plug

Is there a possiblitiy of having the wrong head gasket? Perhaps the correct one is thicker. I've seen that on the Sea Doos. They have different head gaskets to increase or decrease the volume of the combustion chamber.

 

[HybridMX6]

Re: Double Fire Ring on spark plug

It is possible someone has shaved down the block or head to flatten it out and did not compensate for it with the corresponding head gasket. They do make low compression gaskets that are thicker, for that instance.

 

[Joe Reeves]

Re: Double Fire Ring on spark plug

The Champion QL77JC4 plugs, gapped at .040, are the correct plugs for the 1973 115hp Evinrude as for many other hp models.

As above, someone has either shaved the heads/crankcase, OR the powerhead has an internal problem (piston play). See below.

(Piston Play Check)
(J. Reeves)

This procedure will tell you if there is any wear or play in the Wrist Pin, Wrist Pin Bearing, or Connecting Rod to Crankshaft area.

Remove the spark plugs. Insert a screwdriver, dowel, punch, or some object of your choice through the s/plug hole and into the cylinder/piston area. Hold the tool lightly against the top of the piston. Turn the flywheel by hand, bringing the piston up to top dead center, then continue turning the flywheel to pull the piston down about a inch..... all the while holding the tool lightly against the piston top.

Now, at the point whereas the piston has been dropped down about a inch, grab the flywheel and hold it firmly. Now, push that tool solidly and firmly against the piston top.

If the piston moves without moving the flywheel, there is a problem (wear, play, clearance, etc) somewhere with the items mention in the first sentence. Be sure to check all of the pistons/cylinders.

 

[bansheetaz]

Re: Double Fire Ring on spark plug

i have a 73 115 johnson with the same problem. #4 cylinder piston hits the spark plug with QL77JC4 plugs. i have no slop in the wrist pin or crank shaft. no knocking in the engine. runs great. i just need to double up the gasket washers. wierd.

 

[Vic.S]

Re: Double Fire Ring on spark plug

Just a suggestion for what it is worth. J4C or J6C are shorter reach plugs (3/8" rather than 1/2" ) and would solve the problem! Perhaps worth a try.

They are not inductively suppressed like the Q plugs (but probably any NGK plugs you tried were not either unles the number began BZ...)

BTW you should not use resistor suppressed plugs eg Champion RL.... or NGK BR...)

 

[Faztbullet]

Re: Double Fire Ring on spark plug

The correct plugs are the UL77V surface gaps for that engine, The BRP website and spark plug list only lists the L77J4 plug for special app's only. This is why they are hitting piston

 

[Joe Reeves]

Re: Double Fire Ring on spark plug

There are thousands of 1973 V4 engine out there running with the Champion QL77JC4 or L77JC4 plugs, gapped at either .030 or .040 without this problem existing.

 

[Faztbullet]

Re: Double Fire Ring on spark plug

Dont want to argue that it could be so.. but the 73 was a motor all to its own as it used different rod and piston than other 115's as wrist pin location is different and rod is different (longer if I remember correctly) and BRP site lists UL77V as correct plug for that model. Also here is link to current BRP spark plug chart and it does not list the 115, but the 115 is the same as 135 of that year and it list UL77V or L16V.
http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf

 

[bansheetaz]

Re: Double Fire Ring on spark plug

so what do i do? the ul77v foul quite badly after awhile to the point where the engine is very hardstarting. it sneezes and kicks the starter so it disengages during cranking. runs great once started though. am i safe to double the washer on #4 cylinder and run it that way?

 

[Daviet]

Re: Double Fire Ring on spark plug

If you have been running it that way and have not had any problems, I would double gasket it and keep on running it that way.