MAN D2840LE401

The engines you're looking at are the very last version of the 100% mechanical V10 in MAN lineup, capable of 820hp at 2300rpm.
It has been a very popular builders' choice for many years, when the V8 was only capable of 680hp, which was not enough for some boats that, on the other hand, didn't need the 1000+ of the V12.
They are widely regarded as solid and reliable, with the added bonus of not requiring any electronic wizard mechanic to fix anything.

They only began to be not attractive anymore when the V8 was spiced up to 800hp in the early noughties, offering a bit better power to weight ratio and also some space saving in the e/r.
In fact, that triggered a power increase also in the V10, initially to 1050hp (LE403), which was MAN's first attempt to introduce an electronic governor, with somewhat patchy results.
And eventually, they introduced the 1100hp (LE423), fully electronic and with common rail injection.
But both only lasted a few years, because eventually they phased out the V10 block altogether, since in the meantime the common rail V8 and V12 covered all the power nodes from 900 to 2000hp.

Bottom line, of all the MAN V10s, in terms of reliability I'd pick the LE401 anytime, assuming that their power is adequate for the boat size/type.
And also the 2600 hours per se wouldn't worry me too much, but it's reasonable to expect some serious maintenance to have been done, throughout their life.
What sort of service history have you been able to check?

In my part of the swamp, a good MAN shop can not be found.
Check out your local MAN shops. A good & clean MAN shop is required.
Not many V10s here in the swamp either. Just a few 8 & 12s.
My dream engine is MANs R6.
I luv them all.

There were some oil cooler and flywheel adapter gasket issues on some engines. Heck of a repair job. I understand those issues were resolved.
Check the engine history and oil leaks well.

Don't try to save the chrome on the rocker covers. Looks good, lost cause.

Reliable, quiet, maybe (maybe) tighter on fuel.
Service and parts are more expensive.

I'm in N Florida. My heavy MAN tech is in S Florida. I order my customers MAN parts from Texas.
Go figure.

When that chrome starts peeling and changing colors, watch out. Formed (O ring like) gaskets are used for rocker cover seals.
Oil will start seeping past these gaskets between the monkey metal and chrome.
The nature of the two machine screws that hold the rocker cover down will not allow for more tension on the gasket/seal.
Been here a few times.

Find that better MAN guy for your engine surveys.
Oh, sorry an old OhNo gen-set on board. Maybe can negotiate a lower sell price.

I have owned a pair since 2007. Very good engines if you take care of them. I would say by now if the turbos have not been rebuilt they will need to be done, same thing for the fuel pump. Of course we assume the owner kept up with the scheduled maintenance of periodic cleaning of the heat exchanger and intercooler, and injectors (atleast pop test them). Try not to be affected by the MAN dock talk particularly concerning the 820s. A good shop is a must. Where will the boat be located if you buy it?

It was a sister ship to yours that I started my wild MAN ride.
Lot of my blood spilled in that bilge.

I always did the fuel filters first, then the impeller.
All adjustments and repairs while not hot.
Oh, that SR fan is available on Amazon.

Then got the oil hot, pumped it out and called it a day.

Day 2, The oil filters have drained mostly into the engine, pump the drained oil out.
Pull the oil filter plugs
Then pull the filters when not hot and messy.
I'll never understand the luv that MAN has with this style of oil filter.

Oh, those plugs, Find a nice tight 6 point socket for them, long pull breaker bar. One nice snap/yank.
Either the plug comes loose correctly or the threaded adapter comes out of the cast with the plug.

If the later, let me know.

We used Mobil Delvac synthetic 15W40 with great results.
There was not many oils available to meet factory specs.

Fresh coppers and not to tight when back together.

I remembered wrong and typed incorrectly, 5W40 is correct and that's why we had to order and reserve it.
Have not had Hands On for a few years now.

If you ever came across any written MAN recommendation for a specific brand/type of oil, I'd be interested to see it.
In fact, in my experience some MAN dealers recommend one or another brand (mostly Shell or Mobil around here, but not only), I suspect based just on what they find at cheaper drum prices.

All I'm aware of is that the official factory standard is either M3275 or M3277, for pre-common rail or common rail engines respectively (see attached "Approval Codes" abstract).
So, for your common rail engines, any M3277 compliant oil should be fine.

Now, I'm not sure of what brands are or aren't available in the US, but the latest MAN list of M3277 approved oils that I'm aware of is 7 pages long...!
I'm also attaching it for your reference.

PS: FWIW, I also use the Delvac for my non-CR engines, but the MX which is less expensive than the synthetic, while being still M3275 compliant (not M3277, though).

Glad something works.

I remember now applying a dab of tef-gel to the plug threads and fresh coppers.
A smart tug and they would came out next service.

Those same copper washer seals are used on small ZF oil banjo hoses and fittings.
Still using them up. I had to purchase a bag of them years ago. Still have a 1/4 bag left and using them on lots of lil projects.

I made a special 5 gal bucket to catch the last filter oil while I pumped the sump of the overnight drained oil.
Hot air gun formed it with a flat side including a tilted lip. Conforming flat to the engine bed / stringer.
When I popped off the cans and filters, they went rite into the bucket also, no mess.