Councillor O'Connell says the Mary River is rising and three more low-lying businesses will be affected by the next high tide around midday (AEST).
The river will peak around seven metres early tomorrow morning.
Councillor O'Connell says the businesses were hit in the Australia Day floods and the owners were in the process of rebuilding.
"The marina businesses ... are well prepared," he said.
"In fact, the marina businesses I'm referring to, the building that they occupy, never got reoccupied since the last flood, so it's a shell of a building."
Local disaster coordinator Mal Churchill says residents in flood-prone areas are being advised to leave as a precaution.
But he says there is no reason to panic.
"Be prepared in the event that they do need to evacuate - it's probably easier to go early than leave it until too late," he said.
"There's a history of flooding in Maryborough and a lot of these residents are well aware of what they need to do.
"The last thing we need is for panic.
"The prediction is for seven metres - the previous flood here went to just under 11 metres, so we do have that four metre leeway."
Meanwhile further north, weather bureau forecaster Peter Otto says Bundaberg will miss out on the worst of the rain today.
"It might cause some concern to residents, but the hydrologists don't believe it's enough to add significantly to the river levels, so things are easing off."