First I feel I should mention again I'm only "familiar" with these engines, living on the coast I'm surrounded by them, their owners and the repair & preformance technicians that tinker them - but I don't own one, I've never had to break one down or figure one out & TBH I'm not a big fan of outboards in the first place lol
What is the reasoning to the changes in oil? Is there better power off the line or something with the thicker or thinner mix?
Goes off to read the link now.
On pg54 you'll find the general specifications for the engine family:
http://www.yamaha-motor.com/assets/service/manuals/1/lit-18626-07-03_1417.pdf
...however, I may have made a poor decision to include that monstrous beast in the convo - while I wanted to provide the full range of oil use to balance the "200:1 @ idle" reference, the fact is that thing isn't even remotely a "typical" two stroke, it's far more like Davezilla was theorizing then anything even close to what's usually known as a two stroke engine.
It's actually almost exactly what you were thinkin' of Davezilla... sort of... as I understand the Z300 anyway.
The HPDI (High Pressure Direct Injection) VMAX series first forces it's oil to the crank & bearings without any fuel mix, the lower piston ring has a bypass/grooves that allow oil past to lubricate the top piston ring and upper cylinder - so essentially it's "oil/fuel" mix is blowby. The "mix ratio" amounts referenced is more regarding overall consumption rates then actual fuel/oil/air mixes.
Now while this is all sort of similar, it really isn't even remotely applicable - this thing is likely as close to a full-out racing engine as the general populace can just buy. For example it's fuel injection is provided by twin high-pressure fuel pumps delivering an incredible 1000psi - your typical automotive "high pressure" fuel pump provides about 100psi in contrast, low is around 10.
Ofc there's the engine control module (ECM) system as well with sensors that include crank position, throttle position, engine temperature, air temperature, fuel pressure and even atmospheric pressure, which is used to continually adjust the ignition timing, fuel mixture and more... even still this thing consumes something like 50-60
gallons of fuel per hour @ high cruise.
...direct injection, ECM control, etc - all familiar it's true but perhaps not to quite this extent or scale, particularly with two strokes. This is insofar as I'm aware close to the pinnacle of commercially available two strokes, very much closer to Formula One racing then the 'smokers we all know and love - any even momentary 25:1 oil ratio comparison would be much like thinking 28x10-17 Hoosier drag slicks might be needful or help a Huffy launch faster lol
Jus' for the lols - water makes for a really effective muffler so even if you've heard one of these beasts in passing, they don't seem all that rude. Forced into the confines of a cowling, they don't even seem all
that impressive in size... but if you've ever heard one of these beasts hauled out & being prepped ashore for the spring/fall seasons, you'll likely understand why I made the F1 comment heh
After a bit of hunting I found a clip - but bear in mind this is "only" the 250hp and the guy's phone mic utterly fails to capture the earth-rending screams;
http://youtu.be/XEq7jGzsB54
Come spring I'll try and remember to grab a vid of one of the VMAX 300 'smokers waking up & getting ready to devour everything in it's path, it's a truly awe-inspiring sound that'll move any motorhead to thoughts unclean, even if you don't care at all for "stinkpot" boats
edit: Jus' to be sure, all of their 25hp & under
premix two strokes are a constant (obv) 100:1 - which is much, MUCH closer to our relevant scale & needs then the "exotic" but amusing 300hp examples