big trouble i think, hoping

[silentfaith]

hiall, i have a trawler that has the old round datamarine depth and speed.

all the rest of my tronics are raymarine so i found out that the transducers are 250khz which is called for raymarine, so i bought working raymarine st40 depth and sd40 speed. ok,,,, so
the seatalk cable on the back of the st40s are my power and just plug in.

now, i cut the transducer cable off of the old depth unit (about 4'' from the plug in on my datamarine depth) and **** it is different than what the raymarine plug in area on the st40 depth. it has 3 slots, a black, a red and a uncoated wire.......the transducer cable i cut has what looks like a tv cable, tinned wire twisted around a plastic tube with a single copper wire inside. hoping someone can help me figure how to get that transducer cable hooked up to the back of my st40 depth. tks cpt.craig