2001 Yamaha 250 outboard cuts out

[Mikeboater]

2001 Yamaha 250 Saltwater 2 series Outboard cuts out intermittently when running hot. Runs fine then cuts out and has very weak spark. Starts again when cold. Found shorted wire by ECU and fixed but did not solve issue. Am a car mechanic but not that familiar with boat engines. Little more information- I figured out the shorted wire was B+ feed to oxygen sensor heater circuit. When the engine would not start it flashed a code 19 'low voltage' but yet cranked fine and fast.