RE: RC Boat to take out a line fishing line - your wisdom needed
ManDownUnder,
The distance may/will be a problem for normal RC radio equipment. I have no idea what is available/legal for you 'down there', so no help with that.
Some of the fishermen here use a block of foam hollowed out to hold a automotive/marine battery and a trolling motor. The distances they work with are quite a bit shorter than your's and they use a 'jerk-line' instead of RC, but there's no reason you couldn't use radio control. There's a company that makes floating docks here so large 'chunks' of foam are easy to come by. In Australia? 'Nuther one of those 'no idea' things for me. Guess you could always make one. There are a number of ways to attach the fishing line to the boat, just depends on how elaborate you want to get. The simplest is just a tube at an angle on the boat. Drop the fishing weight into the tube. When you stop the line from paying out, it's pulled from the tube.
There are a couple of manufacturers that make 'fishing boats' but they are probably much smaller than you need, and certainly not inexpensive!
Good luck...
- 'Doc
PS - All fishermen are crazy so this isn't exactly an unexpected idea, right?