Guys I had a similar incident with a new to me 2017 Yamaha SHO. I was cruising at WOT and really wasnt watching the rpm guage at the time but she shut down instantly and swamped up pretty good. Still shifts gears, trys to start for about a 1/2 second and nothing. Got towed in and looked under cowling when home and I cant turn the motor either way with a pry bar. I had no alarms, I didnt smell anything, had water pressure earlier in the day but like i said its a new to me boat so I was looking at all sort of stuff yesterday in my first official fishing outing in the thing. Tell me if yall think Im missing anything or if I can answer anymore questions that may help diagnose. Im hoping its fuel issue but man I dont know.