I decided to do some digging at a Champion Spark plug website and learned the difference between these plugs:
- Both have low-resistance inductive radio noise suppression.
- The QL82C is a hotter plug than the QL77JC4, so may be better for a lot of slow trolling.
- The QL77JC4 comes pre-gapped at .040
- No pre-gap spec on the QL82C was given.
- The QL82C has a “J-Gap”.
- The QL77JC4 has a “Cut Back” gap.
- All other dimensions, etc., are the same for both numbers.
If anyone is interested in looking up specs on these or any other Champion plug number, I found them at this site – just put the plug number in the “Search by Part number” box and the specs will come up.
https://www.championautoparts.com/find-my-part.html