Man Diesel 2940LE403

The first thing you need to do, Find a real MAN shop, Go talk to them.
Ask around the dock who works on their MAN stuff.
If you don't like them, go talk to another real MAN shop.
But you will need a REAL MAN shop to talk to, work with and who does not drag their feet when you call with an issue.

Then, have that real MAN shop survey the engines well.
Get an estimate what it will cost to bring the engines up to correct standards while he is there.
Your going to need this when countering the selling price.

IMO, If the seller does not have logs, records, receipts; it didn't happen.
MAN engines have a service schedule.
MAN service can get expensive and many owners do not get it done.

I bring all this up; There is not a good MAN shop in my area. Heavy MAN service comes from way out of town.
There are some pukes that will work on them around here but there is not much nice to say about them.

IMO, MAN engines are great. It will be your support that makes/breaks that greatness for you.
Heat exchanger service is pretty critical on these also.

When you do some searches here on YF about that V10, you will feel good.

Also, boat sounds familiar, Search YF for MAN Viking also.

+1 to everything CR already said, with an additional warning.

The 1050hp D2840LE403 (not 2940) is one of the few "transition" MAN engines, which is neither mechanical (as was the LE401, much more popular but only good for 820hp from the very same V10 block), nor fully electronic with common rail (as was the 1100hp LE423, the last development of the V10 block before they phased it out completely).
This makes the LE403 it a bit of an "orphan" engine, because its electronic governor was only adopted for a few years, before MAN fully jumped on the common rail bandwagon.
Consequently, even among MAN dealers, it's easier to find either "old school" guys who know the mechanical engines like the back of their hand, or the new generation of (usually) younger mechanics familiar with all the electronic gizmos, but mostly focused on common rail engines.
So, what you should look for is not only someone familiar with MANs, but also with this particular engines family, so-called EDC in MAN jargon (as opposed to CRM, which are the much more widespread common rail, still in production today).

BUT, I believe the peculiarities of of these EDC engines are only in their specific, short-lived electronic management.
Which is good news, because AFAIK the other parts - like the turbos, CAC and HE that you mention - are much different from other models, and therefore they should be very well known to any MAN mechanic.

There is nothing that jumps out like an "Achilles Heel" to me on any MAN engine. That is not to say they may have personality.
Proper maintenance is the only way to stay on top and harness the MAN engine.
A false MAN tech is your "Achilles Heel".
Any good tech can change oil and clear debris from a cooler. Be aware, there are some that can not do that.

Do me a favor, contact Performance Diesel, ask them who is their preferred shop is in your area.
These kids installed most factory engines and covered their warranties. This is a good start.
https://www.performancediesel.com/

Sorry, correction of my previous post, where the bit in red got lost in typing...

Out of curiosity, at which age and hours clocked approximately, if you don't mind me asking?

I can assure you that they are the latter, because the former never existed!

OTOH, the listing mistake makes it very easy to google for the boat...
...Which as far as can be said from the photos, looks very well maintained indeed, e/r included.

All the very best for a satisfactory finalization of the deal!

PS: by the way, my question which you quoted was actually addressed to what motoryachtlover said of the turbos in his '95 boat...

I see, thanks.
Can you recall also the running hours (ballpark) they had clocked by then?
Besides, how did you notice the problem, have you got turbo pressure gauges?
Or was the performance noticeably affected?
Thanks again, it's very nice to have an idea of what I might expect in a few years also in my boat...!