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Dave nicholls28/04/2012 08:38:18
16 forum posts
26 photos

Hi shipmates, I am building a small search and rescue boat, the motor being used is a Graupner 400 speed 7.2 volt, with a current drain when stalled of 21 amps. Can i use a viper marine 15 speed controller to work with the above motor?

Regards, Dave.

ashley needham28/04/2012 20:49:08
7036 forum posts
206 photos

Dave, tricky question. As the current draw on a 30mm prop will be well inside the max current value for the ESC and so it will run quite happily. If planning to use a larger prop then you will need to use an ammeter and see the current draw.

BUT if it stalls and you keep your finger on the full forward button whilst cursing and twiddling the stick of wood, things may get a bit warm, or even blow up.

A sensible person will see that the motor has stalled and not do that ,so takes your choice!!

In answer to your question then, I would, the next poster on this thread probably wouldnt...


NB. If I HAD a 15A Viper already, I would use it, If I had to BUY an ESC as I didnt already have one, then I would get a 25A one, can`t hurt.

Gareth Jones28/04/2012 21:43:18
796 forum posts
1076 photos

I would go with Ashley's suggestion but to be on the safe side, fit a 10 amp fuse between the battery and speed controller. If the fuse blows you know you are operating close to the speed controller limit. If it doesn't then Mtronics speed controllers have a current limiter anyway so should not get damaged unless you do something really silly (like reverse the battery polarity).

Just one question out of curiosity, the picture above seems to show several Tornado speed controllers - what are they for if there is just a single 400 sized motor?


Dave nicholls29/04/2012 16:42:34
16 forum posts
26 photos

Many thanks to Ashley & Gareth for information on motor and speed controller problem.

The prop is less than 30mm, i already have the 15 amp controller so i am prepared to give it a go with a 10 amp fuse as Gareth suggested.

Answer to Gareths question on Tornado speed controllers is the picture shows an unfinished wiring job of a boat called Atlantic Challenger, the complete boat is finished now and i am waiting for some good sailing weather. Many thanks to both of you.


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