Are the spark plugs the problem or is it something else? 115hp 73 V4

[teslaman]

I recently trashed my surface gap plugs and installed NGK version of a QL77JC4 with a 0.04" gap. Although the specs call for 0.03" gap, someone in the forum suggested that the 0.04" would help it idle better and so forth. When I took the boat to the lake this past weekend, I couldn't even get it to fire. I took the boat out of the water and removed the spark plugs. After adjusting the gaps to 0.03", the boat fired right up.

My question is this: Is it possible that the NGK equivalent is different enough from Champion to cause insufficient spark? Could it be something with my electrical system? Is a 0.04" gap to big regardless? I'm just curious. I would like to get the best spark plugs for the task if possible.

 

[rickdb1boat]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Put some QL77JC4's Champions back in there and gap them to .035 and see how it does. OMC's do not like NGK's...

 

[jtexas]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Don't know what it is, but there is a difference, and champs work better than NGK in OMC motors.

But the spark plug gap might not have been the only variable in your experience last weekend; did you try to start the motor out of the water before you regapped the plugs, and did you launch it again after?

Also, did you have any kids with you? In particular, a 7-year-old nephew that might have been exploring your helm, pulling out the kill switch lanyard without you noticing? Don't ask me how I thought of that! Maybe he put it back while you were fiddling with the plugs.

 

[imported_lorin]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

I seriously doubt if the brand of spark plug matters. There must be hundreds of thousands of OMC's operating with NGK's around the world. Champions aren't available everywhere.

 

[rickdb1boat]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

You can doubt it, but it's true...The manufactuer doesn't recommend them for nothing...

 

[jtexas]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

The previous owner (my dad) had put NGK's in my '79 right before I got it...the center electrode wore down at an alarming rate...they didn't last the summer...champs go a couple years or more...that's just my own experience.

 

[tschamp20]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

ive got the same motor as you tesla,w/ champion plugs and wont start either gapped at .040.at .030 she purrs like a mad angry lion,on muffs anyway.thats a good thing by the way.
did it run good after regapping to .030?

 

[teslaman]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

I'll definitely get some champion plugs then.

jtexas, I didn't try to start the motor until it was in the water. When it didn't start I pulled the boat out of the water, adjusted the plugs to 0.03" onsite then relaunched the boat.

Should I try champions with 0.04" or should I stick with 0.03"?

 

[Johnson110]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Gap set at 040 , motor will idle better!!!

 

[R.Johnson]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Sound's like the ignition sensor's need to be regapped. That ignition won't notice a .005 -.010 plug gap. We're talking 30-40,000 volt's here.

 

[Texasmark]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Agree with RJ. 40,000 volt ignition with microsecond rise time. I had one car that had a .06 gap and coil didn't put out that much voltage. But I realize that in a marine environment you are firing a usually cold cylinder and have an oil contaminated plug.

Mark

 

[Texasmark]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Never did figure out about why the surface gap type plugs unless it it long life. I had a 115 I6 Merc for about 7 years and never changed the NGK surface gap plugs and she ran like a screaming banshee.

Mark

 

[papasage]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

surface gap is good for W O T but cant burn a lot of oil . easley fouls

 

[teslaman]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

my problem with surface gap plugs is that they easily get crud between the concentric electrodes which shorts out the spark. Of couse, my motor is dirty inside. Although I have decarbed, it still builds crud. Probably aging head gaskets or something like that.

I'm switching to the standard type because the electrode configuration minimizes this buildup of crude so I can start the thing without having to remove and clean plugs.

 

[teslaman]

Re: Are the spark plugs the problem or is it something else? 115hp 73 V4

Boy! Champions are hard to find around here! Anyway, I've located some QL77JC4's at the local O'reily's. The guy on the phone there said that the new part # was 828.

Anyway, I'm going to pick some up today and install them tomorrow at 0.04.