Hi, I have been reading the beginning of this thread, albeit now 3 years back but most interesting on the motor choice discussion.
My Elke kit which is still as dispatched from Graupner, and during its life it has gained a 280 motor. I mostly have low powered model boats and these days many of the esc's have an overload cut out. So at the bottom end as I am re current consumption I have not fittted a fuse or ever had a burnt out motor.
My son and I many years back now used to run Bobby's with a 540 and a P40 prop which gave them a healthy turn of speed. Any weed encountered was just chewed up! The only near stalls were caused by picking up fishing line.
In my Elke I am planning on using a prop shop 25mm 3 blade one and either a monoperm or super monoperm with a very cheap esc.
However there are many motors available, choice is not easy, and I do have a liking for using re-cycled commercial motors. As an example I have a twin powered HDML using 2 ex-computer tape deck motors (Pitman now 50+ years old now). The boat goes faster than scale speed and there 2 off 9 cell Nicad packs (they were going cheap) and full speed is just 3/4 of an amp (750mA) per motor.
So I very much agree that a good match of prop to motor can make all the difference to time and performance on the water. I also like to be able to turn the prop and feel the (brushed) motor 'cogging'.