1978 Evinrude 115 HP spark plugs

Mr.Stuart

Senior Chief Petty Officer
Joined
Jul 18, 2007
Messages
701
I changed out the plugs in my 78 115 horse evinrude and went with NGK's, engine didn't run as well with the NGK's as it did with the old wore out Champion plugs, which I kind of expected from reading another thread on the matter.

I looked in the owners manual and the manual calls for either a Champion L77J4 or an AC M40FFX, these plugs are no longer available from what I've found, so what would be a good replacement? I found that with the NGK's I had worse low end performance, it likes to die when running at low idle (ie) pulling into a doc for mooring, it actually ran better with the old champions in it, so I pulled out the NGK's and put the Champions back in it until I can find a suitable replacement.

any ideas?

I'm finding this forum an invaluable tool by the way, the knowledge here is unsurpassed, better then any book, although I've ordered the maintenance manuals for the engine as well, it just hasn't arrived yet.
 

Launcher

Cadet
Joined
Aug 18, 2007
Messages
7
Re: 1978 Evinrude 115 HP spark plugs

Champions are still available.

L-77J4

I have a '79.

Quite an education.
 

Mr.Stuart

Senior Chief Petty Officer
Joined
Jul 18, 2007
Messages
701
Re: 1978 Evinrude 115 HP spark plugs

I just found 4 AC M40FFX plugs through Amazon for $1.69 each and bought them, should be here in a week or so.

I was surprised how much worse it ran with the NGK's, so if anyone wants a used set of new NGK's for dirt cheap, let me know:D
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1978 Evinrude 115 HP spark plugs

you may get the same results with the AC plugs as the NGK. motor was designed to run with champion and they are still available. NAPA auto parts.
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: 1978 Evinrude 115 HP spark plugs

Run with Champion QL77JC4 plugs at .030.

The old plugs have too much radio interference.

http://www.boatsetup.com/SparkPlugChart.pdf

The AC M40FFX and the L77J4 are both listed in the original parts manual for your engine as "*alternate spark plug for sustained high speed operation".
 

Mr.Stuart

Senior Chief Petty Officer
Joined
Jul 18, 2007
Messages
701
Re: 1978 Evinrude 115 HP spark plugs

doing a google search for the origional plugs comes up with the QL77jc4 as a replacement, that apears to be a pretty common replacement for the origional plug
 

Mr.Stuart

Senior Chief Petty Officer
Joined
Jul 18, 2007
Messages
701
Re: 1978 Evinrude 115 HP spark plugs

I'm seeing the .030 gap in the searches, this is a common talked about issue through other boards as well, seems they lowered the gap from .040 to .030 some time ago, everyone is going with the .030 gap.
 

Xdeputy95

Recruit
Joined
Aug 17, 2015
Messages
3
Hello, has anyone tried the AC plug m40ffx? Trying to see if they would be better than the Champion plug for my 78 115 Johnson. Thanks!
 
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