My Bo'Bo' (four axles) Märklin diesel locomotives:

Updated 2009-09-23

Märklin 3074, DB 216 090-1:

Märklin 3772 A, DB 212 225-7:

Märklin 3772 B, DB 212 225-7:

Bo' Bo' is actually wrong for these locomotives, as it is a B' B'.  This means that the two axels in each bogie are mechanically connected.

Märklin 3774, DB 216 127-1:

Märklin 37500, ONTC RAm 1984:

The conversions made to these models:
Märklin
locomotive
number
Motor Decoder Functions Additional parts
Originally
fitted
Converted
to
Originally
fitted
Converted
to/with
3074 dcm 3* dcm 5*
6090
Analog 6090 f0 = front light, changing with direction
3772 A lfcm 3* dcm 5*
60904
6080
prototype
60932
mfx
f0 = front light, changing with direction
f1 = interior light RH side
f2 = interior light LH side
f3 = driving sounds
f3 = shunting speed
f4 = acc/brake delay cancel
f5-f15 = other sounds
456200 holder for decoder
B lfcm 3* no change 6080
prototype
no change f0 = front light, changing with direction
3774 lfcm 3* no change 6080
prototype
no change f0 = front light, changing with direction
37500 dcm 5* no change c91
sound
no change f0 = front light change with direction
f1 = interior light in the cars
f2 = bell
f3 = horn
f4 = acc/brake delay cancel