this is taken from Truncheoneer's Newbie Super Guide at www.mw4online.com. it's the best explanation of damage transfer that i've seen. i hope it helps!
i think the marauder falls in the same category as the thor and the thanatos...since it has a thin center torso, some people might target the side torsos instead.
cj
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>>> DAMAGE TRANSFER -
“Damage transfer” is a very important concept that all MW4 players need to be aware of. When a section of a Mech (a side torso, for example) has had both its external armor and internal structure destroyed (color-coded black on the Multi-Function Display on the HUD), any additional fire that hits the destroyed section is not “wasted” by the attacking Mech. In the case of the destroyed side torso, any additional damage that is inflicted on it is “transferred” to the internal structure of the adjacent section of the Mech, which in this case just happens to be the all-important Center Torso.
The fact that the damage is transferred to the internal structure of the CT, rather than the armor, is crucially important. It is not the destruction of the CT’s armor that kills a Mech. Mechs blow up when their CT’s internal structure is destroyed. If you continue to pour fire into a Mech’s destroyed side torso, you are in fact actually tearing into the internal structure of the Mech’s CT, in effect bypassing the CT armor. Yes, you guessed it: You can take out a Mech this way even if its CT armor is completely unscathed.
Keep this important concept in mind when you are attacking a Mech with a narrow Center Torso like the Thanatos or Thor. Pick a side torso and keep hammering it. Get to know the hard point positions of all the Mechs so you’ll know which side torso carries the most weapons. Might as well go after the torso with the most firepower.
Mechs also blow when both legs are destroyed. When one leg is gone (showing black), damage is transferred to the other leg’s internal structure, bypassing the armor just like the torso sections. If you see a Mech with a destroyed leg, don’t go after the other one. Keep pounding the bad leg, rather than wasting shots on the armor of the good leg.
If a section is green, yellow, red, or dark red, there is still armor on that section. When the section is dark red and blinking, all the armor is gone and the internal structure is now being hit by any fire striking that section. Black indicates the internal structure is gone, and the section is ready to begin transferring damage.
It gets better: If a section, once again a side torso for example, is dark red or blinking dark red, and you hit it with more damage points than needed to destroy the side torso, the extra damage points are not wasted. Any damage points over what is required to destroy the side torso are instantly transferred to the Center Torso!
Note that there are two types of internal structure material: Standard and Endo-Steel. You’ll see the type used on each Mech in the Mechlab armor screen, down in the lower-left corner of the picture of the Mech. Endo-Steel is lighter, which means that Mechs using it have more tonnage available for equipment and weaponry, but there is a drawback to using it. Endo-Steel transfers 100% of the damage from a destroyed section to the adjacent section, while standard internals transfer only 85% of the damage.
Good to know, huh? If you see an enemy Mech with a bright green undamaged Center Torso, but a badly damaged side torso, don’t waste fire trying to strip away that CT armor. Tunnel under it. Go after the side torso instead.