i bought this engine used from a very trusted local outboard shop. it ran fine for a while, recently it started missing, as a result the engine would not plane the boat out. after investigating the problem i found that the middle cylinder is only fireing at five to ten second intervals at a time causing the boat to continuously learch forward as it was missing. i ran the engine in my garage with the lights out and found that the middle cylinder plug is arching around the head where it threads into the engine. i never heard of this before. Since i am very mechanically inclined when it comes to cars and motorcycles this was something new. well i replaced the plug, the spark plug wire and then the entire pack for the middle cylinder. It is stil arching. i then thought perhaps the coil pack is not grounded properly so i grounded it to the block using a 10 gauge wire. it still archs. I am at my wits end. I thought it was fixed,:^ then during a major striper tourmanent it started acting up again. anybody have any ideas whats going on here??? I guess thats what i get for running a 1975 engine. ohh and one more thing the engine runs fine leaving the dock to my first fishing spot but when started again it misses due to arching im assumeing moisture is acting like a conducter and making it arch. any help is much appreciated!