Many DC permanent magnet motors are avialable in the market, biggest
advantage is controlable speed. Go in search and look for "permanent magnet
DC motor manufacturer" and you will find tons of link in there.

Horse power is variable from 0 to 20 or more, its upto you to decide what
horse power you are lookimg. With your kind of project I would think a less
then 1 horspower is enough provided you are using gear to reduce the RPM for
propeller shaft.

If you are looking some thing cheap go on ebay and type "permanent magnet DC
motor" and you can find many under $100. Remember you need dc motor driver
device to control the speed, so do some research on internet before buying
any dc motor.

Another suggestion about batteries, look for deep cycle batteries cauz it
last longer and built to stand for charge and discharge more oftenly as
compare to ordinary auto battery.





"Michael" wrote in message
...
Hi,

I'm building a model submarine it will have a displacement of around 500kg
and a length of 4m.
Having worked out a rough idea as to the size of the motor required, 3hp.
I'm now looking for suggestions. Sites like technobots don't stock ones
large enough and so I'm struggling to find an answer.
Then there is the matter of how to control the speed. Ideally I'd like
proportional control.

So, does anyone know where I can find a large enough motor, ideally with
the
electronics to control it? The onboard power will be provided for by two
12V
batteries,
of which the AH is still undecided.

Thanks

Michael