spark plug gap

[dieselcat]

good morning IBOAT world.....i just just surfing through the new post and came across a thread about spark plug gap,a member had stated that he was going to be doing alot of trolling and didt want to foul plugs while doing so.someone chimed in and said to gap at .040 instead of .030.
my ? is,is there any other advantages to gapping plugs more or less than factory recamendations?such as better or worse fuel mileage?

 

[JB]

Re: spark plug gap

Over the years OMC changed gap recommendations back and forth between .030" and .040" and suggested the wider gap to reduce risk of fouling when running at low speeds for extended periods and the smaller gap for all-round use. On some engines they even suggested different spark plugs for different applications. Many small JohnnyRudes from the 50s to the 70s can use either J4C or J6C Champions.

Selecting different gaps, or in some cases different plugs, can be done on many JohnnyRudes without going outside of factory recommendations. It depends on what model you have and what typical usage you plan.

 

[seahorse5]

Re: spark plug gap

In some situations, a wider gap can cause premature fouling and misfiring. As fuel, oil, and carbon deposits build up on the sparkplug ceramic around the center electrode, they can become conductive and the voltage will bleed off and short circuit to the plug's metal shell. With the correct or even sometimes even a closer gap, the voltage will jump the gap before taking the deposit path to ground.

A wider gap does cut down on hard carbon bridging where a piece may lodge between the electrode gap and shorts out the plug. Sometimes it may look like a black whisker from the ground electrode to the center one.

 

[dieselcat]

Re: spark plug gap

Over the years OMC changed gap recommendations back and forth between .030" and .040" and suggested the wider gap to reduce risk of fouling when running at low speeds for extended periods and the smaller gap for all-round use. On some engines they even suggested different spark plugs for different applications. Many small JohnnyRudes from the 50s to the 70s can use either J4C or J6C Champions.

Selecting different gaps, or in some cases different plugs, can be done on many JohnnyRudes without going outside of factory recommendations. It depends on what model you have and what typical usage you plan.

ok,so what is the difference in the QL77JC4 and the QL82C?These two are the one listed for my motor,will one produce a hotter spark?

 

[dieselcat]

Re: spark plug gap

bump

 

[kfa4303]

Re: spark plug gap

Hi diesel. The "QL" plugs are considered "long" plugs and are not intended for use on vintage OMC motors as their electrodes are a bit too long and can be hit by the pistons. As JB stated, Champion J4C and/or J6C plugs are best. I've used J6C in my 10, 20, 33 hp OMC motors without issue. I would try to stick with Champion brand as well. While there are "equivalent" plugs from different makers, they never seem to work quite right and Champion plugs are readily available at most auto parts stores.

 

[dieselcat]

Re: spark plug gap

guess if id said what my motor was it would help lol.its a 1995 erude 88spl,model e88tsleoc