i have a 93-40hp -j40tlet, am having problem finding champion-ql78c plugs within 50 miles of n. idaho, altho this is what service manual calls for. can i use ngk without causing damage? thanks
I'd stay with the Champion plug. Some OMC motors were more tolerant of incorrect heat ranges but that motor isn't one of them. Especially if it's being lugged. If the 78 isn't available in your area maybe the QL77JC4 is.
