CE emission question

The Recreational Craft Directive is the legislation covering the required European technical standards for vessels <24m for sale and use in the EU, including emissions standards. Details are linked below.

Unfortunately my experience is with the construction and sale of new vessels but it seems import is a much more complex subject. It may be that some type of compromise or limitation on area of operation, time spent in EU waters, restriction on further sale, etc could allow your client to satisfy his primary aims. I'd be very surprised if this ends up being an easy or straightforward process. I'm sure there are agencies that specialise in the legalities although I couldn't list any.

Gardner engines will definitely not meet any current emissions standards. If the vessel were repowered in 2021, the applicable European tier would be Stage IV or V for non-road mobile machinery (NRMM), which I believe is broadly similar to US EPA standards for that timeframe.

https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32013L0053

Sorry it's not more promising info...

A visiting yacht would be much less problematic

Do you know something we don't, for jumping in such conclusion?
I'm not denying that there are better options than Gardner for repowering a 2021 boat, if you're only aiming at market value maximization.
Then again, there are many if not most boaters out there whose objectives are different.
And anyway, for those whose only aim is economic value, I have a suggestion: forget boats altogether!

Maybe the owner is a prepper. One giant EMP and modern diesels might not run. Please wait for me to get my tin foil hat before responding......

On a more serious note, depending on one's use and priorities arguments can be made for a dead simple diesel. If it has fuel and you can get it to turn over it'll run besides being tolerant to damage while still being able to make power.

Just for the records, it's Gardner that used to build marine diesels - gardeners are the folks who grow plants in gardens.

Anyhow, what you are saying is beyond what Judy disclosed, and is also the reason why I asked if you know something we don't (or I don't, at least).
If the above is correct, I wonder how a new boat could have been registered with a non-emission compliant powerplant in the US to start with, before even considering to bring her to Europe.

Regardless, if she is indeed US flagged, I think the only viable option for cruising legally EU waters is entering under TA (temporary admission) rules, that don't need any emission checks, AFAIK.
The main restriction is an 18 months time limit, but that can be restarted simply by moving the vessel outside EU waters (like to Tunisia, or wherever) and then re-enter. And I think TA is only allowed for non-EU flagged boats owned by non-EU citizens.
No idea if that's compatible with Judy's client needs.

Do you mean there's no emission rules all new boats must comply with, in FL?
I'd expect that in Nigeria, if that...

Do you mean life as usual aside from fighting the red flu drinking bleach instead of margaritas?
Anyway, if you enjoy FL lifestyle, good for you.
For me, it was the second US State I visited, more than 30 years ago.
Fast forward to present days, having spent quite a bit of time in about two dozens of others (which I have a funny feeling that many FL residents never did), I consider it as one of the most boring and less authentic places in the US.