If it is a Merk, there is a strong probability that it is the variable
resistor that detects the lower unit position. It is located on the outside
of the lower unit at the pivot point, is about 1 1/4 in diameter and is held
in with 2 screws. There is a similar looking item on both the port and
starboard side, I forget which one is the trailing switch and which is the
resistor. Just take it off and turn the 6 point plastic shaft while
watching the trim gauge. If the gauge flickers, it's time to replace the
part. There may be broken wires as a possibility too, but they are
stainless and very difficult to solder.

Don Dando