Years ago I saw pics of sawn-in-half Yamaha blue 10-micron fuel-water and oil filters on another site (theHullTruth?) and became convinced they really are different/higher quality enough to be worth the small price upgrade. They are NOT re-badged Sierra or Racors.
There seems to be absolutely unanimous support among 5-star techs to use only ethanol-free gas if you can get it.
You can get it almost everywhere, use pure-gas.org and post the price there. (Use GasBuddy.com to find the cheapest diesel or gas).
If you must use etoh degraded gas, add Yamalube Gas treatment or Startron (they are 50/50 on that, so they can't all be shills for the company).
They say on the way back in run at Wide Open Throttle for 30-60 seconds to burn off carbon buildup.
Follow the break-in procedures and add Yamalube Ring Free at every fill-up ($49/qt).
Only use Yamaha 4M 4-stroke oil (a bit more, but like you said, it's a $25,000 motor and no one knows better what to feed it than it's Maker).
I agree my DuraMax will gulp french fries oil biodiesel without a burp and always seems anxious to haul a heavy boat with Mobil-1 or Rotella or whatever the GMC dealer likes, but when it comes to outboards I say go with what The Maker specifies and be happy about it.
SimYamaha.com has good prices including free shipping specials on Annual Maint kits. Andy knows everything Yamaha and is a great resource (he had the part numbers for the stainless continuity wires between the mid/lower sections off the top of his head).
In 4 words, I agree with Brent.
Again.
Surely someday I can find something to dicker with him about, but it may be a long time coming.
Happy Boating!
John