Spark plug Question

[targetpanic]

I pulled the plugs out of my 25hp Mariner. Not knowing the motor's history I went and bought 2 new ones that were the same as what I pulled out. They were Champion L77JC4. I got my Clymer Manual the other day and it says I am supposed to be using L76V which is a surface gap plug. Is the manual correct????????? By the previous owner putting in the wrong plug could damage have been done??? What is the difference between a surface gap and J gap???

 

[achris]

Re: Spark plug Question

If you give us the serial number of the engine we can look up the right plugs for you...

Both plugs were used in the 25 range, just depends on which ignition system is fitted...

The surface gap plugs have no heat range... Running them in an engine that wants j-gaps will make it hard to start, run rough and possibly misfire...

Running j-gaps in an engine wanting surface gap could cause combustion chamber heating problems, possibly leading to a piston failure... Not good...

Chris........

 

[targetpanic]

Re: Spark plug Question

It's a 1993 OD168460.

 

[achris]

Re: Spark plug Question

oh dear!!!

My parts manual calls out 3 different plugs.... BUHW-2, BU8H and BP8H-N-10... and no explanation of how to determine which one to use...

But, my Merc genuine workshop manual says use the BP8H-N-10 (L77JC4)....

So.... I'd bin the clymer and buy a Merc manual...

Chris...........

 

[targetpanic]

Re: Spark plug Question

LOL...nothing can be simple can it!!!!!!!!!
Should I just stick with the ones in there for now??????? Any other thoughts or suggestions?????

 

[achris]

Re: Spark plug Question

Stick with the L77JC4s....