I have a 2000 maxun 3300 SCR with twin 350 efi mercrusierthunder bolt 5 ignition engines. The starboard side engine started to run rough and misfire after 20 minutes of running. The starboard battery gauge would also bounce and jerked with the tach when engine would misfire. If turn the engine off and restart the engine it runs fine for the 1st 3 to 4 minutes after every restart. Installed new spark plugs and no change. Any body have any ideas ?