Spark Plugs Johnson 90 1989.

[outboardkiwi]

Hi, I removed my spark plugs for inspection today from my Johnson 90 1989 J90TLCEM and noted they were p/n QL78YC as supplied by my dealer, the manual states QL77JC4 is the correct plug. Is it ok to continue running the QL78YC's. Thanks in advance. OBK

 

[WillyBWright]

Re: Spark Plugs Johnson 90 1989.

Either/Or. 78 is just slightly hotter than 77. Y means the plug has an extended tip that can help get the spark closer to the middle of the charge. I've never noticed any difference between the two concerning performance or wear. But the extended tip is a bit less prone to foul.

 

[Dhadley]

Re: Spark Plugs Johnson 90 1989.

If you use the QL78YC (extended reach) they can hit the pistons with certain heads. After a WOT run the gap will be about .009". Trust me. If youve been running them already you should be OK but with todays fuel I'd opt for the cooler 77's.

 

[seahorse5]

Re: Spark Plugs Johnson 90 1989.

Dhadley is right in saying that the QL78YC plugs could cause problems. The recommended plug for your motor was updated back in around '95 or '96 to the QL82C. It is more foul resistant than the QL77JC4

 

[Dave Abrahamson]

Re: Spark Plugs Johnson 90 1989.

Not to butt in, but does that go for a 1983 J-90 as well? J90TLCTE<br /><br />Thanks Dave

 

[Dhadley]

Re: Spark Plugs Johnson 90 1989.

Yep, the same. Glad you asked.