Help me start my 2x 1100HP engines!

Well, What engines are they?
Were they pickled before storage?
Those fresh batteries?
Boat stored in the water? Exhaust was open or closed for storage?

Turning by hand?? With a big bar?

Are you expecting intelligent answers if you don’t bother telling us what model engines, what kind of boat etc. impossible to answer.

I know a guy in the UK that would be able to take a look and give you advice as to how to proceed.

Thanks, so where do we find information on "it's a big boat 27mtrs"
Just sayin

Your not going to turn a cold V12 by hand.
Your not going to do it with old batteries.

You did not mention if the engines were pickled before storage?
Or exhaust ports sealed?
This leads to my first thoughts;
Stuck valves in the heads.
Rust on the valves and valve seats.
Rust on the cylinder liners.

There is a service opening on the flywheel cover that accepts a MAN engine turning tool.
A 1/2" (12mm) bar or large ratchet can turn the engine over from here.
Don't poke a pry-bar in there and try, damage to the flywheel teeth will result.
Using this tool offers a nice ratio turning the flywheel. You can move the engine over but can feel if something is wrong, like a stuck valve or piston.
Then you go pulling rocker covers and heads.

If you can get more than 2 turns with out any crunches, prime some fresh fuel filters (w fresh fuel), load up some fresh batteries and start them up.

The mechanical MAN V12s are popular over here. Not a lot of them but those that have them are very happy.
Be ready to change the engine oil promptly.
Send coolant, fuel, and oil samples to your lab promptly.

Don't forget to check out your clutches and raw water pumps.

You're right, we don't really need any information to solve your problems.

How about checking the starting batteries first? Have you checked voltage to see if the batteries even have anything in them? I’m guessing they’ve been sitting for years too based on first post?

I'm not referring the front of the engine, the engine/clutch adapter that I call the bell-housing that covers the flywheel with starter ring.
A tool attaches to a square hole. With gear reduction, takes little effort. Just slow.

On some I have worked on, a cover and tight access blocks the front of the engines. The frames and other junk gets in the way of swinging a tall bar.
Oh, it was a MAN engineer that turned me to this also. Further, the more reliable timing marks are back here.
If you can reach yours, great. The reduction on this tool will take a while to turn the crank twice.
But you can still feel the restriction. Been there, yep, dropped valve. Saved that piston.
I luv single heads.

Now on my V-12 Detroits, That is where to turn the crank from. Lots of room.
A pipe on the end of a breaker bar and I can move the crank with lil effort and precision.

Well, Sale pending on that boat.
I kind of liked that super long look.

I had to register if I wanted to see more than the first picture.
So,,, I did not see any more pictures than the first one.

I wouldn't even attempt to turn the motor over with the battery or by hand without pulling the injectors first and lubricating the cylinders with some diesel or etc and leaving it in there overnight, and then trying to bar the motor over by hand.