Hi again Richard,
My 'Joffre' runs on 6v, 7ah sealed lead acid battery. I have fitted a brass prop, and use an Mtronics 15amp ESC. (originally a Bob's board!!! almost antique now!) My motor is a 6v Decaperm, somewhat expensive these days, but as it has been in the boat since I built it 25 years ago, it has proved its worth beyond any doubt! With this setup I have run in our club's mini-marathon of an hour's continuous running at full speed, having been pottering about all the morning on the same battery previous to the afternoon's marathon. At the end the motor was just slightly warm, and the battery still had plenty of life left in it. Hope this has been of help.
Danny
PS With regard to the question ref stick position on the Tx, you have to set the Mtronics ESC up the first time, detailed instructions are included, and yes, if your wiring is the right way round, centre position is off, full up on the stick is full ahead, fully back on the stick is full astern.