I have a 2003 Mercury 150EFI and have had problems with plug fouling issues. This is what I’ve done, all these parts are new. Coils, crank sensor, both fuel pumps, reeds, had injectors cleaned and checked and still foul out the plugs on port side in less than 15 min. It used to be all the plugs would foul out, but since I opened the wiring harness and check for any bad wires now it’s only the port side that foul. Now the starboard side are burning nice. And also new thermostats. I think the only thing left is the ECU, but having a hard time finding anyone who can fix them, been told for that year there’s no parts available to fix. Any help would be appreciated and thank you.
