I have AC MR43LTS plugs in my small-block (Vortec) Chevy jet bass boat. Nobody carries them around here without charging $30+ for 8 of them. Can't I use the auto versions? I don't use my boat in salt water and they get wet in car engines anyway with rain, snow, etc. and work fine. What differences are there between marine plugs and auto ones? I also can't find the equivalent in an NGK or better quality plug. Any suggestions?