Originally Posted by JonL

Sorry you don't like it!
I don't know the particular valve timing events for a MB diesel engine (I should look it up...) but there is most certainly an overlap period. In fact, a diesel could tolerate a much "hotter" cam than a gasoline engine for three reasons:
1. There is no throttle, so the scavenging effect will not be spoiled at light loads... the intake vacuum will not attempt to keep the exhaust in the cylinder.
2. There is no gasoline in the incoming fresh air charge, so there is no possibility of raw fuel going out the exhaust during the overlap ruining efficiency and raising emissions.
3. The exhaust has a lot of excess air (unlike a gasoline engine), so some exhaust dilution of the incoming air will not cause misfiring the way it does in gasoline engines.

V-6 gasoline engines are rarely used as marine engines anymore because they had chronic problems of aspirating sea water in through the exhaust exactly because of the phenomenon I described.

If there is any restriction in the intake, the negative pulses in the exhaust will be amplified.

At cranking speed, the air in the exhaust will be moving at low velocity and under low pressure. It will behave as a nearly incompressible fluid. Any suction generated at an exhaust port will be transmitted throughout the system.

If I can get two helpers tomorrow, I'll try an experiment. One to hold the "stop" lever, one to crank the engine, and I'll hold my hand on the tailpipe.