Be aware of how much noise or smoke your engine, generator or diesel central heater makes outside. Do not run these next to houses or near another occupied moored boat if there is the possibility of intrusion of noise or fumes.
On Canal & River Trust waterways, engines and generators must not be run after 8.00pm or before 8.00 am. (Canal & River Trust Boat Licensing Terms & Conditions). CRT Byelaws also prohibit the running of engines in gear (ie the turning of propellers) whilst moored up, at any time, to avoid damage to the bank, wharf or walls.
Neither of these rules preclude arriving at or departing from a mooring, or travelling along the waterway (but be aware that boating at night is not always allowed by insurance companies, so please check your insurance policy. In particular, hire boats are generally not allowed to boat outside hours of daylight).
On other waterways, please check the licensing terms and conditions and byelaws for the relevant navigation authority.