If I buy a CE marked boat from Europe, does it have to be UKCA marked?
In 2021: No. Theafter: Yes.
The UK will continue to recognise the CE mark during 2021, so as to give the UK industry time to issue all the UKCA certificates required. From 1st January 2022, UK will not recognise CE marks: a UKCA mark will be required.
That said, the reality for private buyers (importers) is not as bleak as it appears. The UK-EU trade agreement has a section on technical barriers to trade which explicitly requires both sides to appoint conformity assessment bodies using accreditation to the same rules/standards and same degree of scrutiny. This is so that both sides may trust the work of the other.
This means that if the boat is certified as compliant with RCD by a European Notified Body, UK Approved Bodies are expected to respect this and not exploit the private importer by making a full re-assessment for UKCA certification. So a used boat would subject to a visit to check to confirm it is the boat that was certified, has no (apparent) modifications and is not exhausted. This would incur a cost but not a full assessment fee.
Note, however, that boats which are not (required to be) certified may be treated differently. In the absence of a certifier’s testimony, an UK Approved body will need to conduct a fuller assessment since the builder’s compliance regime may have been untested.
In the other direction: the EU stated, long ago, that it would not recognise the UKCA mark.