It is about 55km's to Fitzroy Lagoon or 50km's to Musgrave form the bar. According to your figures that gives you 50km's of fishing range, that is a fair bit if you hang around the reef.
There is quite a bit of ground on the way out to the reef as well. Areas like the Inner and Outer Wides or 8 Fathom, you can do a day trip up to Bustard Head and fish the rocks that come out from the headland or troll the headland at 1770.