More than 100 volunteers and three helicopters are involved in the search in the Burcher/Lake Cowal area, police said.
The 49-year-old man was last seen about midday on Friday and was reported missing early on Saturday morning.
His car and boat trailer were found in Burcher, but his boat was missing.
Police divers have been called to the scene of a submerged boat spotted from the air late on Saturday.
Flooding eases at Forbes
The Bureau of Meteorology said flooding at Forbes was easing although an evacuation order was issued for low-lying areas of Condobolin as flood peaks on the Lachlan River move downstream.
In Wagga, streets have been closed in the Flowerdale district as the Murrumbidgee flowed into the area, with the river expected to peak at 6:00pm on Sunday.
Rain is forecast in the area, but not expected to dramatically affect flood levels.
Flooding continues to affect large areas of inland NSW with warnings current on the Peel and Namoi Rivers, Macquarie, Bogan, Murrumbidgee, Narran, Warrego, Paroo, Barwon and Belubula Rivers.
A minor flood warning is in place for the Murray River upstream of Lake Hume.
