Heh problem with the weight is it's totaly stripped out (no more electronics/motors just a bare hull) so it'd be slightly inaccurate lol!
I posted this vid a while back, this is it on 12v http://glen.botclips.net/hacknqd.wmv
Regarding RPM of the motors, not quite sure, they're just standard cheapo 550's so i'd think around 18000rpm or so, not sure if it was getting to that in the water though.