MATT. without  filling up valuable forum bytes with endless lists, the Cornwall model boats site lists a few Graupner motors or I dare say there must even be a Graupner website, which will have the definitive answer to things technical in it.. There is a bit of power and rev difference between these engines…what sort and size of boat are you building and what are you going to use it for…racing / personal amusement / must be faster than fred`s P.T boat ..???  Ashley

Matt, good point. I think the 8.4 or 9.6 is what the motor is designed to run at for optimum efficiency, I suspect their amp consumption at max efficiency is at this voltage. HOWEVER physically the motor will run at the other voltage 14.4 or whatnot. Obiously the power output will be better and the revs will be more at the higher voltage, but I suspect not neccessarily say, twice the 9.6 figure at say 18v. The run time really depends on how much the motor is loaded as well as what voltage you are running it at. An ammeter and a bunch or different props would be required at the pondside to get that max efficiency, but for max performance one suspects the max allowed voltage would be required.   Ashley.. there must be some fast boaters out there?? I am a slow boater personally.