The engine in question is a marine ford sabre 225. Id imagine any large bus/truck engine would be similar.

Dad called to pcik my brains on boost control and while i know how normal automotive petrols control their boost levels, I was stumped on this one.

Engine runs up to revs with the boat lightly loaded, making mid 20s psi boost pressure.

If the boats loaded up with divers etc, engine runs round to 40psi and wont come up to full revs.

Its one of a pair, the other behaves fine,this one did before a rebuild last year.

Apparently there is no sign of an actuator or lever for an internal wastegate, nor any pipework or external wastegate...

Do big diesels somehow control boost by adjusting the fuelling? Or are we missing something?

Cheers