check your wiring
st60 will have a 5 way connection as the following..
red : speed +ve
green : speed signal
Brown : thermistor
white : thermistor
A bad thermistor, or lack thereof will not be the problem, it is not required to be present for speed to work
.. if your speed log is a combined speed/temp then there should be ~10kohm between brown and white.
check there is voltage between red and screen
, this is the supply the goes to the paddle... cannot recall
the exact voltage you can find it online..i *think* its about 6V or so
If you can pull the transducer
, the voltage between screen and green will go from 0V to the voltage previously measured for every 90 degree movement of the paddle wheel
it IS possible you have a bad transducer
.. mine died two years ago...but certainly check the wiring
first.. and, if necessary, you can cut the cable near the transducer and install a terminal block.
The other outside possiblility is that if you dont have SOG on the seatalk
then its a possibility that your ST60 has defaulted to reading SOG vs Speed... this is a dealer setup config.. and the natural default for the instrument.