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[Peterm]

Someone has already given the simple , reliable solution which I use regularly.   Use two 6v 4aH in series to get your 12v supply, tap off at the centre for your 6v supply.   Pete M

[sweeper]

Well said Peterm,
I've been watching this thread as various suggestions have been put forward. I'll leave the subject of the various ESC's to those who have experience with them but I will add one comment. The suggestion of using simple Ohm's Law to evaluate the current taken by a motor is incorrect. If you consider the basic operation of a motor you will realise this.
Need proof? Apply an Ohmeter to the terminals of your motor (off supply) and note the reading. Connect your motor to it's normal battery and check the current taken while running on no-load. Now apply Ohm's Law. You will find that there is a difference (often considerable) between the calculated current and the current taken in operation.
I'll not go into the theory of the why and how it happens - after all as someone said "all you want to do is get the boat working on the water".
Hope this helps someone. ???

[Fast Electricals]

Measuring the DC resistance using a multimeter will not give an accurate answer. When the motor is spinning, it produces a back EMF which opposes the current flow from the battery. The static resistance can be used to calculate stall current but little else.

Neil

[sweeper]

I think you may have misread my suggestion. The idea of the reply was to show that you could not apply a simple Ohms Law calculation to a motor, as had been previously suggested.
Yes, we know all about Lenz's Law and back emf, my idea was to keep it simple without going into the realms of electrical theory.
Most people who aren't into motor theory cannot understand why a machine with a low ohmic value does not take a high current ie as it would appear to if they simply applied Ohms Law to the question.

[Made it to 80 (25p Richer now)]

Blimey I thought this forum was all about model boats not advanced physics where did I lose my way ??? ??? ???

[dougal99]

Blimey I thought this forum was all about model boats not advanced physics where did I lose my way ??? ??? ???

Watford - 1968

[sweeper]

Advanced physics? nah, you need an ology to do that stuff (and I ain't got one of them).
This is just the stuff that young 17/18 year old boy electricians have to learn.