Michael,
You should seriously consider Andre's advice. I know it isn't a 12V
solution, but it is the best one especially if you should use the complete
drive and control electronics. They are available used in junk yards at
scrap prices. Contact me off-line if you want more info.
Steve

"Michael" wrote in message
. ..

"AndreL" wrote in message
...
Find a used GE engine from a Golf cart. Some provide 11 HP at 48 volts
while the most common provide 3 HP at 36 volts. This is way enough for
your submarine because compare it to a 15 ft aluminum boat with two
anglers aboard - a troller engine can push the boat easily.

Just by curiosity is this remote controlled or wire controlled ? With a
camera or for fun ? do you have a website that shows construction ?

"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

Remote control, with a camera and for fun. No, not yet, and progress is
very slow, send me an email at SubAquaModel (join
together) and I'll update you if you like. Planned finishing date is late
2007, so a while yet.

Thanks for all the replies, I get back to you about what I decide