Why take chances? My outboard is the single most expensive item on my boat to replace. I use the recommended oils and greases it calls for. I service it otherwise as recommended too. I want it to keep me going on the water and not cause me to get towed back to a ramp. And cost Lord knows how much to get repaired!
I've seen the current fuels ruin many smaller engines i.e. lawnmowers, trimmers, pressure washers etc.. The internal gaskets, fuel lines and other parts get ruined relatively quick in them. It may take a little longer but, outboards don't have any claim to being unaffected. Even cars and trucks show the effects of todays fuels.
Many, (if not most) people spend tens of thousands of dollars on their boats. Why after that, would anyone not spend a few dollars to replace fuel lines as recommended? Recommended fuel lines @ $25.00 or any fuel line @ $8.00.......IMHO it's a no-brainer!!