spark plug discrepancy

[ab1]

'93 Johnson 150 GLETR

The service manual calls for Champion QL77JC4 but I have also seen that QL78YC should now be used. Apparently this was updated and applies to 94 and up motors, so I should stay with the 77's since I have a 93? However a few plug charts I have seen have the 78's listed for 91 and up?? Are there pros or cons for either. I want to stay in spec and use the right plug that will not cause any problems.

Just need to know which plugs to use on this '93. It has NGK's in there now, which need replaced regardless due to age.

Thanks in advance for any direction you guys can provide.

 

[ezeke]

Re: spark plug discrepancy

The current BRP recommended plug is the Champion QL78YC; no NGK or other brands are listed.

 

[ab1]

Re: spark plug discrepancy

The current BRP recommended plug is the Champion QL78YC; no NGK or other brands are listed.

Thanks...that's what the plug charts show and I don't like having the NGK's in there so want to get the correct replacements.

I'm confused why the OEM manual suggests 77's but it has since changed... Is there a difference in these plugs? The 78's are 'longer and hotter' based on the very limited comparisons I can find. Is this a good thing?

 

[gsyfishy]

Re: spark plug discrepancy

I recall something about the age of the motor in regards to the 78, I have a 1991 and still use the 77, but they are becoming more and more scarce to find cheap.

 

[tashasdaddy]

Re: spark plug discrepancy

there is almost no difference in the plugs. either is really correct. if you do a lot of trolling QL77JC4 is a better plug, with the gap adjusted to .035, which helps eliminate carbon build up.

 

[ab1]

Re: spark plug discrepancy

there is almost no difference in the plugs. either is really correct. if you do a lot of trolling QL77JC4 is a better plug, with the gap adjusted to .035, which helps eliminate carbon build up.

Thanks! I don't do much trolling...more of a go fast, stop and fish with trolling motor, go fast again type of boating. I do get out often with the kids so we'll go slower and some of the lakes have significant areas of idle only or 10mph. Really just general, recreational bass boating with a handful of tourneys each year and a bunch of lazy days on the water with wife and kids. I'm just looking for whatever fits best and causes the least potential for problems. This considered, would you go with the 77 or 78 and at what gap? I'm thinking the 78 at .30 per the updated charts, but the oem manual says otherwise.

 

[ezeke]

Re: spark plug discrepancy

With all due respect, the updated factory recommendations usually have good reasoning behind them.

CDI also makes specific recommendations; see the service note in the installation instructions for your specific powerpack here: http://cdielectronics.com/InstallSheet/113-4986.pdf

 

[ab1]

Re: spark plug discrepancy

With all due respect, the updated factory recommendations usually have good reasoning behind them.

CDI also makes specific recommendations; see the service note in the installation instructions for your specific powerpack here: http://cdielectronics.com/InstallSheet/113-4986.pdf

You guys are the best! I figured the updates had a valid reason but I found via google that one of the updated johnson/champion charts had some errors. Didn't want to take a risk and I knew you all would have the answer. I'm going with the 78's at .30

Thanks also for the link to the cdi .pdf...that might come in handy one day. Filed for reference.

Again, thanks!!