QL77JC4 or QL78YC w/ '89 V4 120 Looper

[kitebuz]

I purchased an older boat ('73 Formula 233) w/ twin 1989 Evinrude 120's. I am going thru them doing basic maintenance - new water pumps, head gaskets, T-stats, & plugs. They ran fine, but just wanted to make sure everything was good (& turns out there were no T-stats). <br /><br />I got 8 x QL78YC's before thinking to research this site - just told the shop what engines I had & needed plugs.<br /><br />I have seen recommendations for both plugs. Is one better than the other for these engines? I will use it for general boating in the ocean, and some trolling. Will do most of my running around 4000-4500 rpm. <br /><br />Don't know if it makes a difference, but these engines have the updated T-stat assembly.<br /><br />Thanks.

 

[WillyBWright]

Re: QL77JC4 or QL78YC w/ '89 V4 120 Looper

I've never noticed any difference in performance between them. The main difference is that the 78s have an extended tip (Y) which gets the spark further away from the head. Is that an advantage? Idunno!

 

[marinemech1]

Re: QL77JC4 or QL78YC w/ '89 V4 120 Looper

ql-78yc is now the recommended plug

 

[kitebuz]

Re: QL77JC4 or QL78YC w/ '89 V4 120 Looper

Thanks, guys. I guess I'll use them, and not worry. The Evinrude chart (http://www.boatsetup.com/SparkPlugChart.html) shows the QL78YC for 1994 Engines and newer, but I have read other use them interchangeably w/ the QL77JC4's. A little confusing, but good to know others have used them w/ no issues.

 

[Dhadley]

Re: QL77JC4 or QL78YC w/ '89 V4 120 Looper

You can use either. I prefer the 77's in mine because they're a bit cooler and the tip isn't on top of the piston. Both means the combustion temp is a little cooler and may help with todays fuel. Either will work fine.<br /><br />I too have ran both back to back in my looper (recreational) and seen no performance difference at all. We do see the slight difference in the race motors.

 

[Walker]

Re: QL77JC4 or QL78YC w/ '89 V4 120 Looper

I too use the 77's. They are available everywhere down here. $1.49