I did a quick search of your posts to find what model 140 you have, with no luck. The only one that's dufficult to find is the V12, as it is hidden under the cover on the top center of the motor, that small plastic cover that I believe the MB star is on.
If it is an older 6 or V8, it's under that large round metal lid with the large black plastic knob securing it. If it's newer, it had a black plastic reservoir with a fairly large cap with the dipstick attached under the cap. It should show where everything is in the owners manual.