I have been collecting spark plug information from the experts on this forum (e.g. racerone, faztbullet, joe reeves) in an attempt to understand whether I should be running the Champion QL77JC4 plugs in my 1986 Johnson 150 crossflow V6 (J150TXCDC). My OEM service manual
only mentions Champion UL77V surface gap plugs. However, I troll a lot more than I run at fast speeds.
In regard to the QL77JC4 recommended spark plug gap, Joe Reeves once said, "You can use either the L77JC4 or QL77JC4 plugs and gap them at .040 . I know some manuals say to gap them at .030...... trust me, set them at .040. The "Q" indicates a suppressor plugs that is designed to help eliminate noise (ignition splatter etc) from interfering with any electronic equipment.
JoeReeves QL77JC4
Again, I only have my OEM service manual to reference and no other technical service bulletin info from Johnson to verify the QL77JC4 usage in my engine. I'm just trying to sort this out for my engine and thought I would share the .040 gap info.