Editing Electric boat (section)

===Electric motor===
{{See also|Magnetohydrodynamic drive}}
[[File:"e-Tolly" bildge, a 1973 Tollycraft Electric Retrofit.jpg|thumb|An example of an electric retrofit. Two 9&nbsp;kW LMC motors powered by 16 Interstate deep-cycle 6-volt batteries.]]
A wide variety of [[electric motor]] technologies are in use. Traditional field-wound DC motors were and still are used. Today many boats use lightweight permanent magnet DC motors. The advantage of both types is that while the speed can be controlled electronically, this is not a requirement. Some boats use AC motors or permanent magnet brushless motors. The advantages of these are the lack of commutators which can wear out or fail and the often lower currents allowing thinner cables; the disadvantages are the total reliance on the required electronic controllers and the usually high voltages which require a high standard of insulation.