[TorpX]

Originally Posted by Sniper297

Only files I find with the word "pumps" are all *pump*.ogg which are sounds.

If you mean the datablock in zones.cfg file;

Yes, that is what I mean.

Any clue what flotability should be rather than zero? My guess looking at the flotability of other objects would be whether or not the object floats and how well it floats, which an engine or pump wouldn't.

I seemed odd to me, also. That's why I mentioned it; it really isn't intuitive. I would try a few small (positive) values. It may not do anything. There certainly SHOULD be something we can use to adjust the pumps, after all.

Here is part of a post about it (for SH3, of course):

NYGM HummingBird
[PumpsXXI]
Multiplier=1.0
;Flotability=0.15 ->> Original value
Flotability=0.005 ->> change this value
.
.
.
Changing the Flotability to the above value I got the sub to sink about 50m over 12 hours which is sort of acceptable. The funny thing is that the sink rate is not consistent, and will even rise a little at arbitrary depths, but the sub generally sinks, albeit much slower. A speed of 1 knot will keep you more or less at constant depth at 245m, but you'll need two knots or more to bring the sub up.
Still testing and playing around...