MAN V10 - 1050hp LE403s

I can't answer your question on the exact RPM cutout.
But I half recall to have been told by a MAN chap that it depends on both load and RPM, so you might be looking for a number which is actually variable.
Any MAN service should be able to confirm you that, anyhow.

BUT, and I'm mostly talking to Beau now, the 820hp version of the V10 (aka D2840LE401) was fully mechanical.
And as all other MAN mechanical engines, it didn't have any cutout system.
It is indeed rougher than the V12, and to a lesser extent also than the V8, particularly at low RPM.
But that's the nature of the beast - nothing to see with cylinders cutout.

I'd be glad to, if only I could find any references about it.
Can you possibly enlighten me?

Well it seems that we are all going by what we were told...
Coming to think of it, years ago one dealer did mention to me the partialization on just one bank.
But afterwards, I had a chance to speak with the chief engineer of the official MAN distributor, before actually buying a MAN-powered boat.
He's the one who told me that there's no cutout on any mechanical engine.
And since he's the person in charge of arranging training courses for the dealers' network, I took that as Gospel truth.
But I never checked that first hand.

BTW, I can't actually think of how to do that.
What do you think, maybe checking the temperature with an IR gun pointed at each cylinder exhaust port?
Or can you think of any other trick?
I might give it a try on my V8s, the next time I'll run them.

PS: ref. roughness at idle, Beau, I didn't say that the V10 aren't smooth, I did say they are rougher than the V12.
Ever tried a V12 powered boat? You'd be surprised by how smooth those beasts are.

Well, just what I said, that in terms of smoothness the V12 is the smoother of the lot, followed by the V8 and the V10.
And this is something I witnessed on several of engines, both mechanical and CRM.
I'm not objecting to your perception that your engines run smooth, but trust me, you would feel some difference with the V12s (less so with V8s).

I'm not insisting on my previous "no cutout" comment if you had an opportunity to double check that with your expert.
I'll do the same with mine on the next opportunities, out of curiosity.

But I can safely confirm you that there's no way injectors can be "closed", in your engines (as well as any other MAN pre-CRM).
In fact, I've seen them removed and tested, and I also know first hand how the HP pump works.
The injectors are very simple mechanical devices, which are not controlled in any way, other than by the fuel pressure.
As soon as the pressure reaches the preset level (280 bar, as I recall), they pop open and the noozle sprays a burst of fuel - end of it.
So, the only way some cylinder can be cut is by not sending any pressurized fuel to their respective injectors.
I believe that this can only be handled by the HP pump - though at the moment I can't figure how exactly.

On the other hand, you are certainly right in saying that there can't be any "unspent fuel" passing through the cylinders which are being cut, for the very simple reason that if their injectors would squeeze any fuel, there would be no cutout at all!

I own 820’s as well and I was under the assumption that they did indeed have the cylinder cut out feature. May or may not be true. I will also confess that I don’t find my 820s very smooth at idle, but it is not an issue.

I am not sure that I have cut outs or not. Just that I was told that by a few that should know. At idle if you stand on the dock next to the boat and you can see little ripples in the water coming off the hull. I also believe I have noticed what I consider more shaking of the engines than you would see with a gas engine, all of this is at idle. Above that she smooths out. I hope I have adequately described it.