Purchased secondhand, replaced speed controller and had loads of fun till original motor gave out. took 12 months to finally find a suitable replacement motor, as Robbe no longer produce/supply a 600/21 motor, they now only supply a 540 series. So after several attempts with different motors, have finally satisfied myself with a speed 600 race unit. Goes ok on 7.2v, bit nippier on 8.4v, but hold on to your hat and try runnin' 11.1v lipo ! it behaves just like the real thing on smooth water, but be prepared to shift the battery forward for rough/choppy water, so it can still let the semI surface props bite properly.
27/7/12. Have now opted for 11.1v 2200mahr lipo and it goes like stink ! What an absolute flyer, people keep coming up to me and asking what size brushless motor Ive fitted, its that quick. (Motor: Graupner speed 600 race) (ESC: m troniks) (10/10)