I recently refurbished an old (20years) boat that I had built. It is ca 50 cms long, hard chine and fast! Originally powered with a cooking 540 (Weren't they all?) and either 6 or 8 1200 Nicads, she was really fast, turned beautifully and was a pleasure to drive. The propellor was a Graupner P35 and she would run flat out for about 5 to 6 minutes. No speed controller, simple on\off switch.Motor and batteries got warm but not hot.
Well had a mad moment and stripped out the old motor and switch and installed a 23 turn ,540 size motor, 2,4 amp Nimhs and ESC.Kept the same prop.
Does it go? Well yes, but only for about 1 minute or so, then she slows drastically, remains drivable for a couple more minutes before having to be brought in. The motor gets very hot, the Batteries warm. So, thinking about it I would say she is over propped, any ideas before I order extra props. No model shop, have to be postal and so increases both time and costs. Remember this is just a fun project, so not looking for the last fraction of a knot.Just want a reasonable running time with a good speed. (Aren't we all!!??)