"Not sure where the sticker ca
"Not sure where the sticker came from - the service manuals covering all the 40 horse models during that period call for 50:1
Yamaha was the only mfg successful at producing a 100:1 outboard and even though they build or provided parts for many of the Merc models, there was not a Merc model rated for 100:1 - at least one that you pre-mixed.
OMC also had a couple years of 100:1 motors in the late 80's - they found it to be a problem and issued a statement, that could well apply to any motor (aside from the Yami's so designated).
You can decide for yourself, personally, I would be running 50:1 if you use the motor for anything more than trolling...
A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)