Spark plugs L77JC4 or QL77JC4, which is better?

[merc20076]

What is better to get if I run my outboards for trolling speeds? I have a 1983 7.5HP and a 1977 6 HP now in a good running condition but I want to get new spark plugs. They have currently L4's.

Can't wait for spring to get it running on water.

 

[boobie]

Re: Spark plugs L77JC4 or QL77JC4, which is better?

I can't tell which plug is better but I'd refer to manufactures latest specs.

 

[Barnacle_Bill]

Re: Spark plugs L77JC4 or QL77JC4, which is better?

The only difference is the Q which means it is resistor-CDI. Idoubt you could tell the difference in running.

 

[Vic.S]

Re: Spark plugs L77JC4 or QL77JC4, which is better?

QL77JC4, gapped at 0.030" are the currently recommended plugs for both models. QL86C are also listed for the 7.5 and for trolling may prove to be a better choice .

Originally the '83 7.5hp would have had QL77J4 or L77J4, and the '77 6hp L77J4 ( or possibly AC eqivalents). Both would have had 0.040" plug gaps

The Q indicates the that the plugs have low resistive, or inductive, suppression. Ordinary resistor plugs are not suitable for the OMC CDI ignition system on these engines so if suppressed plugs are used they must be the Q type.

The C indicates copper cored electrodes. They replace the old non copper cored plugs which are no longer available

The gap was reduced from 0.040" to 0.030" more or less across the board some years ago but if they run better at 0.040" use that.