Spark plug question for 175 Johnson

[JJB]

I have a question about which plug to use . The manual said to use Ql-78yc but for oil injected to use QL77jc4 . The bombard site list the QL -77jc4 as a optional plug . What is the difference in the plugs and what would you guys run in a 2000 175 johnson . Thanks for the input

 

[angus63]

Re: Spark plug question for 175 Johnson

I use ql78yc in my 95 175 opro. Ql77jc4 run a bit cooler. Either will work fine as long as motor is not modified, wot timing is correct, carbs are clean, fuel is fresh 87 octane, and oil is tcwIII. I originally had 77's when I got the motor, but changed to 78's when OMC changed recommendations. No change in performance or economy.
Good luck

 

[Gary H NC]

Re: Spark plug question for 175 Johnson

Take a look at the spark plug chart,Looks like that year uses only one model plug...None that you mentioned...

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

 

[Dhadley]

Re: Spark plug question for 175 Johnson

As mentioned the 77's are a bit cooler which I like. The Y in the 78's means extended reach. Personally I'm not a fan of them in that motor in recreational use.