Marcus-spark plugs for omc

[charger19]

In an earlier post you mentioned using plugs of the properheat range.I have been told to only run ql77jc4's.Can you explain what plugs to use?Is this something for just the rcers at high rpm(6000+) need to worry about?I'll check out your site, too.Thanks

[racer]

That is the right plug, next hotter is a ql78yc but you should not need this.

[charger19]

Always appreciate your help.Does the ql78yc cover the rest of the omc rpm range?Don't need any numbers, just curious.

[racer]

NO

[Markus]

Charger19,

The heat range of a plug indicates how hot it gets.

If the plug is to "cool", the insulator does not get hot enough to clean off deposits and the the plug gets "fouled".

If the plug is too "hot", the center electrode melts.

The range where the insulator stays clean is very wide; several hundred degrees, so it is not that difficult to find the right plug.

A useful thing to do is to test some other manufacturers' equivalents of the plug recommended for your engine. Then you may get a plug that is just slighly hotter or cooled. As an example, the NGK B9s of my Yamaha fouled bad, making jetting extremely difficult. I tested an equivalent, a French plug called Eyquem, from a discount automotive dealer. Turned out they stay really clean without getting too hot.

[Flat Out]

My 95 Venom uses L82YCs. Most older loopers run L77JC4s. I put a set of L82s in a 73 65hp looper and they definately burn cleaner and don't foul as easily.This may be due to the fact that the motor is probably a little on the tired side and the hotter plug seems to help it. I haven't tried L82s in a Xflow yet. My brother has a 89 140 wich uses L77s yet my Dad's 95 130 uses L82s. these motors are basically the same. The L82 plug projects further into the combustion chamber perhaps this why they may work better. Has anybody else switched from L77s to L82s on older motors. Would like to know your results , starting,low speed ,top speed , general operation.

[rocko]

I just uncrated a brand new 60degree omc powerhead & it had QL77JC4 's in it. I've run them in my crossflow & never noticed any difference in those & L77JC4's

[racer]

Flat out,

The factory has recommended replacing the QL82YC with a QL78YC.

[84exciter]

the "q" is a resistor plug,that's all

[Flat Out]

I've run the L82s in the Venom for 300+ hrs. with no problems. Has OMC given any reason for the change. I don't mind switching but I'm curious as to why they have moved back to a colder plug. I know they have changed plugs frequently in the past few years.