R/C Naval Combat

They should, if you pick the right one. The hard part is choosing properly.... The lack of complete motor curves and pump characteristic curves makes the choosing part a bit of a pot luck... I tend to believe that the outrunners are probably better for our purposes (I could be wrong) but they do slow down when running under water more than the brushed motors (more drag from the water due to the outer case rotation on the motor)

They will draw less than a comparable brushed motor, if properly chosen, they will draw more if improperly chosen.

I have run them on propulsion, and I liked it... it does throw the standard gearings out the window, though. Keep the bearings oiled or replace them with stainless ones.... I also coated the stator with oil to inhibit rust. With no brushes you can do that. I am going to be testing a small brushless motor on a small pump for my light cruiser after I build the pump... we will see how it goes..

Does anybody know at what speed pumps run relative to drive motors? If they work for drive motors, and we know the pump typically is faster/slower than a drive motor, couldn't we make a good educated guess? (as far as what Kv rating to get)

Most of the time on a BB or BC the motors are geared down 13 to 35 so the props spin slower. Say a motor spins at 10,000 RPM. The props spin at 3,700RPM. The same pump more runs direct so the RPM are 10,000.
Most guys use a Traxas Stinger motor to run their pumps. This set up draws about 20 amps and pumps about 2gal a min. Some use a Traxas Titan motor they draw about 24 amps and pump a little better then 2gal a min. So you trade power for pumping.
For a small BC or BB some guys use the standard 550 motor. Draws about 10amps pump 1.4 gal a min

Hey Bob, what voltage are you pumping and amperage numbers accurate for? 6v? 7.2v? 12v?

The amps I have messured are at 6 volts. Some of the pump out times were at 7.2 volts. They were not faster then 6 volts. But the same motor was not used for the different voltages.