That link is poorly written but noise nuisance can occur at any time. After 11pm there is a greater presumption of the need for quiet though. Having said that, councils can ordinarily only address noise nuisance from static premises. Noise from cars or boats or general noise in the street would be dealt with by the police as a breach of the peace or by way of a specific injunction.
Having said all that, it's probably worth contacting you local council's environmental health / noise nuisance team. In some cases, although they have no legal powers when it comes to boats, they may be willing to act on a discretionary basis by sending out an official looking letter, which often does the trick.
May I ask what canal or river this boat is on?