I have what seems the exact same issue right now. Boat is on our lift, I was putting the lift down, trimmed the motor down, no issues. Stopped trimming it down, went to start it, would not start, now unable to trim the motor at all on the throttle, also unable to trim using the switch on the motor itself. Checked one fuse under the helm, checked 5 fuses on the motor, all good. Tried the throttle back and forth idea several times, tried the safety lanyard multiple times, battery tested good on jump box and shows good on boat gage when I turn key on. Are there other fuses that I can check, other ideas? Never had an issue prior to this.
2012 2275GCW 150 hp Yamaha