Here's the best way to get a bow thruster without to much hassle in making up parts...
Cut a tube either plastic or brass/copper to the required outlet size, cut a round disk out of plastic card or brass and glue or silver solder (if gluing use something like epoxy resin on both sides which will make the joint extra strong) it half way between the length this is the divide for left and right thrusting action.
now on each side of this divide drill a hole and tap in a nipple which can hold a rubber tube of a reasonable diameter (6-8mm if you can). so far the cost is minimal as some stock or scrap parts, now for the expense go to halfords and buy a window washer pump ( £10) there normally in a solid black casing, you can wire this motor up to either an esc for full proportional control or on a simple on off system, plug you rubber tube onto the nipples either side of the thruster assembly you created and each end to the pumps nipple input and output, and bingo one bow thruster that cost £10 and can be easily replaced at little cost, the sub boys use these to power there ballast systems in static diving models so im sure they can vouch for there reliability.
I've included a
real rough doodle of what it should look like so don't get stroppy about it
