Evinrude plugs Is this a problem?

[carbineone]

I have a 1974 Evinrude Lark 50HP and what I have read here the plug should be either a Champion L77JC4 or a QL77JC4..From what I have read rom Champion they suggest the QL77JC4 on the OMC CDI Ignition systems and thats what I have.They claim a non Q plug will let them interfere with the CDI system and may not run right.

The reason I am asking also is someone had Champion UL77V,s in the motor when I bought it and thats not even close to the correct number.I am hoping having the correct plugs will let my motor run higher RPMs as maybe with the incorrect plugs it was running off because of some type of interference in the CDI system from having the incorrect plug and no resistor maybe...Anyway let me know if the wrong plug could make a big differance in performance..Either way I removed the incorrect number ones and put in the QL77JC4 just for peace of mind if anything...Thanks

 

[wilde1j]

Re: Evinrude plugs Is this a problem?

Resistor plugs are for preventing interference in external equipment, like VHF radios, RADAR, etc. UL77V is a surface gap plug and is often specified as an alternate to QL77JC4/L77JC4. Just a completely different type of plug w/o an adjustable air gap. All will work fine and won't likely make any difference in performance, other than the QL77JC4/L77JC4 will probably handle trolling w/o fouling somewhat better. None of the plugs you mention will cause CDI interference, period.

 

[carbineone]

Re: Evinrude plugs Is this a problem?

This is from Champions website,they claim poor performance also if the non Q type are used.Are they full of crap theirselves you think?


Outboard marine Capacitive Discharge Ignition systems (CDI) such as used on some Johnson and Evinrude marine engines require a special inductive type resistor spark plug (such as a Champion Q-type). This is because these type of ignitions systems produces less voltage; use of non-inductive type plugs can cause misfires and poor performance.

It does definitley seem to run better already in the tank with the new Q plugs..The other plugs before were new too so maybe there is something to this...I do not know for sure...The non Q ones sure could mess with the tach I bet though for sure..

 

[wilde1j]

Re: Evinrude plugs Is this a problem?

This is the OMC/BRP recommendation:

40, 48, 50 (2-Cylinder) 1989 - 2001 QL78YC (see note 3) .030

Note:
3. On ALL VRO/OMS equipped motors the "QL" supressor plug is recommended.

 

[carbineone]

Re: Evinrude plugs Is this a problem?

Jim I do not know what the VRO/OMS is but I just know what they say as I quoted on the Champion site concerning my CDI system..I guess the only way to tell is to try the Q ones..Cannot hurt I guess to try them..My motor is not a 89 to 2001 its a 1974 as stated so what is the referance to those late years mean to me that you make.....I am kinda slow to understand,LOL.Thanks

 

[Vic.S]

Re: Evinrude plugs Is this a problem?

The plugs listed in the parts catalog are surface gapped UL77V but http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf gives either L77JC4 or QL77JC4 ( gapped at 0.030") as the latest recommendation.

The QL77JC4 is the same as L77JC4 except that it has an inductive ( or low resistance) interference suppressor.

Use the "Q" version if you do not want to suffer or cause radio interference.

What you should not do with OMC CDI ignition systems is use plugs with ordinary resistive suppression such as RL78YC or any other "R" series plug, including things like NGK BR7HS.

Non suppressed plugs can cause interference with the alarm circuits on engines with variable rate oiling (VRO) or oil metering systems (OMS) so the "Q" series plugs are recommended for those.

For a detailed technical explanation of the need for inductive suppression rather than resistive suppression see http://members.iinet.net.au/~pauldawson/iame26-spark-plugs.PDF

 

[carbineone]

Re: Evinrude plugs Is this a problem?

Yes the ones that were in there are what you are reffering to as sufrface gap.How the heck do they work?I have never used one of those surface types before in anything...Was that type of surface gap even around in 1974? I guess I do not understand how they work or if they are better than conventional type plugs?...Thanks

 

[wilde1j]

Re: Evinrude plugs Is this a problem?

Sorry got the wrong year range:

50 1971 - 1975 L77JC4 or QL77JC4 .030

I would use the QL77JC4, but either are fine. The note is referring to two OMC oil inject6ion systems (later than your motor).

 

[tashasdaddy]

Re: Evinrude plugs Is this a problem?

how they work spark jumps from center to the edge. the plugs easily foul. they are basically high speed running only.

BRP recommends QL77JC4, here is chart
http://www.docstoc.com/docs/4877037/Spark-Plug-Application-Chart-for-Evinrude-Johnson-Outboards-thru

 

[wilde1j]

Re: Evinrude plugs Is this a problem?

Surface gap plugs have been around for many, many years. I had a '73 135HP Evinrude that called for UL77V plugs. Never had a fouling problem, but eventfully began using L78V conventional plugs, BC they idled smoother.