What sort of brushless motors do you intend to use?
I say this because one of the things that seems to limit their use in submarines is:
- tend to be very high revving (gearboxes!!?)
- too many to choose from.
I asked a similar question to the Sonar members at the Dortmund show and they said that they tend to have them specially wound.
Are there easily commercially available brushless motors which would do the job?
For example, how about this one :
3508-380KV Turnigy Multistar 14 Pole Brushless Multi-Rotor Motor With Extra Long Leads
I have never used a brushless in a submarine yet but this looks compact and low revving because it is multi pole.