93 Evinrude Intruder starting problem

[jimeng]

This started out as a key switch problem - I thought. Motor wouldn't start initially. Finally started and then wouldn't shutoff with the keyswitch. Replaced the key switch and it was ok. It was time for the spring tune up so I ran a can of engine tuner through the engine and let it soak overnight. It wouldn't start the next day, so I put a new set of plugs in and it started ok and ran perfect. A week later it wouldn't start. I checked the plugs, wiped them off and it started. So, sometimes it will start and sometimes it wont.
When it does finally start, it runs fine. At WOT sometimes, it will miss just slightly. When I back off no problem and it doesn't do it all the time. I have been wrestling with this issue all summer long.

A little more background. I plugged off the oil injection and have been mixing oil in the gas almost since I bought it new. I still run with QL77JC4 champion plugs. I have read that the spec was changed to a different plug. I don't think that is the problem because that is all I ever ran in it, but I am beginning to think I may just need to change plugs again.

When it finally starts there is more smoke than normal and it stumbles a little before it smooths out. It seems like it's not firing, but it will eventually start. Sometimes I will just keep spinning it over till it starts.

This motor has been very reliable for years. Always started easily any time of the year. I am about ready to put it in the shop, but I really hate to. I can do almost everything that needs to be done to it, but I lack test equipment for most of the electronic testing.

Any ideas? Anyone ever experience this?