Crews are back on the waters off Marie Curtis Park (near Brown's Line and Lakeshore) in the city's west end today.
A four-metre fibreglass boat was found capsized in the lake on Sunday evening but a search of the water found no sign of anyone.
Investigators say the key in the ignition was switched on and the throttle was completely open.
The vessel also had two life preservers left on board.
The boat is described as black and white with an older 65-horsepower Evinrude outboard motor.