I Have a 1990 Johnson 120 VRO that has always started and ran fine. VRO removed and running mix for years. New clean fuel both main and aux tanks. No air leaks. 100+ PSI compression and good spark all 4 cylinders. This season I cannot get up to WOT. Fired it up on muffs at idle and started pulling off plug wires. Found two cylinders on starboard side showed no difference (change in RPM) when pulled. To check if this was a fuel/carb related problem I swapped a starboard and port carb. No difference. Same two cylinders not working. Since I have good spark and proved it is not a fuel problem, could I have some type of timing issues? I?ve read some postings about a mysterious blocking diode in the wiring harness. I?m an electronics guy by trade so testing it is easy. Just cannot imagine why this would mess things up unless it has something to do with timing. Again. Spark and fuel. Any advise would be greatly appreciated as July 4th week is approaching quickly.
