Hi, we have VTR 250 turbos on our boat. I notice there is a line with a small cock from just underneath on the inlet casing and it runs to the camshaft space of the engine. It is attached to a pipe fitting drilled onto a camshaft cover. We got 4 turbos and some of them cocks are open and some are closed. I checked and there is a small amount of vacuum on that line.
Looked in our manual, could not find anything. Could anyone tell me what it is for and if it should be opened or closed.

have no experience with VTR T/C , but my guess that it may be the labyrinth seal vent.

Hi,
It may be that it acts as a crankcase breather and sucks all the oil fumes from the crankcase, (the camshaft oil freely drains down to the crankshaft and vapours will freely rise up).
This will maintain a slight vacuum in the engine when running, according to some engine makers doing this or fitting a crankcase extraction fan to mantain a vacuum will prevent a crankcase explosion. It will certainly prevent oil fumes venting on deck from the crankcase breathers and should fractionally improve fuel economy because you will be burning the oil in the engine! It will also help to lubricate the inlet valves.
Check to see if your pipe is connected into the oil seal or the air space.

BP