Hi Shan,
According to my book there are three ramps in Macksville. All suitable for boats up to 5.5m and all of average quality.
The better two are listed as "east side of road bridge (300-400m) on the south bank. Ramp = Fair, Parking = Poor, Concrete 1 lane.
"West of road bridge (50m) on north bank. Ramp = Fair, Parking = Good, Gravel 1 lane.
Hope that helps.
Reefhunter