I am going to get flak for this but afaik for low voltage supplies when a
charge pump is not available, low saturation bipolar bridges are cheaper
and perform better than homebuilt VFET ones. The reason is that the FETs
can't be opened properly with 4.0..8.4V usually available in models.
(Exception taken for logic level FETs which can).

If you want good performance at low voltage, use a driver chip and/or
build your own on-board gate voltage booster. You need to put about 11V
to the gate of inexpensive low Rdson FETs to achieve their Rdson.

For boats the reversing relay and single transistor driver was the most
successfull afaik. Boats do not reverse that fast, and you can get an
automotive 20A relay cheaply. This and a single 50A 0.03 Ohm FET will go a
long way on water, even racing. Also if you do not want propeller braking
put a series diode to the motor. The bridge or single FET conducts in both
directions and it will brake the boat using the motor as a turbine when
you remove drive.

Peter

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