RE: Aquacraft Mini Rio
You can roll up to post #70 or so for how to loosen up the rudder linkage so it doesn't break the control arm the first time you run the boat (or try to).
You're likely to break a rudder bracket or an arm before you break a prop.
An octura x431 prop is 1mm larger and gives a little more speed, but you can accomplish the same thing by allowing your NiMh pack to top off on trickle charge overnight before you run the boat (of course, you can always opt for both ;-). If you let the charger top off the battery pack, you'll have less of a problem with radio glitching or short range.
Remove the left rudder for a little bit more speed. Move the battery pack as far forward as you can without allowing it to hit the drive coupler. This helps the boat get on plane more quickly and it keeps it from looking dorky when your're bringing it in once the pack has run down.
Take the time to roll back through the thread