Man initial idle not in sync

The only 800hp MAN engines available in 2012 were the CRM R6, which normally were equipped with the MMDS displays.
If this is the case, the reading should be pretty solid regardless of the placement.

But personally, I would still waste 15 bucks for a chinese laser tacho, which are amazingly accurate.
Not that I'm expecting the MMDS readings to be wrong, but it doesn't hurt to check.

Anyhow, to try to answer the OP question, I believe that adjustments (if feasible) require the dealer diagnostic system.

Yes, I believe the idle is still computer controlled.
My BD subscription just expired.
If there is a long lag time and they do sync up, it may be sensor fault issue. Still, needs a proper tech plugged in.
I remember up to 10-15 seconds before MANs came to set idle when cold. Maybe 5 seconds when warm.

Like the CAT 3406, I am a big fan of the MAN in line 6. Lots of HP can still be achieved here. Minimal crank distortion means a long life engine.

CR, as I recall the sync doesn't engage at all, under 1000 (or whatever) rpm.

When you run each of them alone, are they running just fine?
If yes, even if 30rpm isn't exactly negligible, I'd be tempted to not bother...

Not using engine sync. Computer sets the idle speed.
When you come in / out of gear, it may take up to 5 seconds (warm) before the engines settle on idle. If they are off, ya got call the kid with the lap-top.

Ok, I understood that by lag time you meant after turning sync on.

Thumping from the exhaust or really out of sync with each other.
My Bert thumps at idle under certain hull levels (exhaust ports level or down) that strums in my ears.
I remember a Nova Tech 80 that drove me crazy with under hull exhaust thrumming at idle.

I would have sweared that the engine sync function is only available above a somewhat higher than idle rpm, regardless of whether gear is engaged or not. But it's been a while since I helmed a CRM powered boat - If you say so, I take your word for it.

Not sure if you can put these controls in sync at un-loaded idle. Never had to try.

Ah, the later kinky (rotary) shifters. I know what you mean here.
BUT, the OP says on start. Is this starting the engines and at idle, out of gear??

Good note here.
Never looked at idle load before.
I'll have to check this my self if I'm ever on another MAN boat.
I recall on some other post we talked about alternator loads affecting idle speeds. Wonder if this is could be an issue here also.

Probably need more info from the OP on all of our thoughts.