Well I just don't know what to think
I could not hear any detonation @ 35 degrees and 93 octane Maine gas
I watched the outboards open and they stopped at about 3/4 of the way for a second then went completely open but I could not see the rpm at the same time
The plugs were clean
The motor had a good idle even down low at 750
The motor ran very smooth thru the whole range
The only thing I noticed out of the norm was when the throttle was shut down I got a long puff out of the carbs