Started diesel with exhaust valve closed

[fatherchronica]

My dock neighbor started his diesel yesterday without opening the exhaust valve. He said he heard what sounded like a backfire and the engine quit. I helped him reattach the riser as it had come apart and we tightened several hose clamps on the exhaust that were dripping. Then he tried to start it and it wouldn't start. At that point, dusk, I went home. I wonder what sort of damage he could have done.

[Sailmonkey]

was the engine turning over? did you drain the water from the water lift?

It's possible, though not likely, that the extra back pressure caused an exhaust valve to not close and it struck the piston........who knows.

[fatherchronica]

We did not drain the riser, but the engine turned over. No hint of starting though.