"United Electric" is my name for this odd detachable boat motor.
Below is the only mention of this motor I have come across. United Motor Industries was involved with cycle cars and add-ons to autos. I believe it became the first company in the UK focused on auto accessories. I read in Peter Card's book, Early Vehicle Lighting, that "United Motor Industries was a predatory company set up to encroach on the profitable motoring accesories market. ...Its success was limited and little was heard of the company after 1914.".