Evinrude?

We also tried that, and it didn't work.
The problem is that now you sit with a spark plug that is not fully tight.
The entry "start" of the tread and the lenght of the thread on the spark plug gives "say" 10 turns to tight, now to clock it you may need a 180 deg turn back. Result loose spark plug.

The next thing we are going to have a very close look is the entire fuel delivery system, from the tanks right up to the injector nozzles. Something has aged or is worn and the computer doesn't pick it up.

For my mate this is becoming a VERY expensive learning curve

 

the local rent a boat guy uses 2 cyclinder ETEC s on his fleet. He says they are great..no problems. His boats run 4 or 5 hours a day..4 or 5 months a year and recieve great abuse.. THE PROBLEM is that the injection, ignition system is complex and not possible for us normal people to understand and trouble shoot. This is true with almost all of the modern outboards and its a curse. The trusty carberated, smokey, fuel hog two strokes of yesterday are so simple that I never bring them to a technician for service.

 

Yes I dream of finding a 18 or 35hp OMC twin in a crate from time to time.

 

Yup..a Johnson Seahorse twin...those engines were tough and so simple that I could fix one with a precise hammer blow.