Gary Warner wrote:


When a sub dives to a certain depth, is that depth
measured from the bottom of the sub, the middle,
or the top. In other words, if it dives to 200 feet,
does that mean there is 200 feet of water above
it or that the bottom of it is 200 feet below the
surface?

Normally "depth to keel."


On modern gas car engines and when it's cold
outside, is it still better to let them warm up a
bit and how warm (how long) is necessary?

RTFM

Anyone have a good way to find the total surface
area of my boat hull while it's in the water? It's
a 22' boat, not very deep V, "square" transom. I
did some estimating, but wonder if there are any
creative ways to get more accurate.

Assuming you are seeking the "wetted area" rent one of those laser
thingys that scan a surface into a computer. Turn your boat on its side
and scan. Read computer generated results.

Rick