My boat is on cradle so cannot help out with ohm readings however...
On my model (1987) the depth sounder cable was joined with a BNC connector under the starboard cockpit locker. This connection was dicey, because of location open to being abused and did pull out. We rewired the connectors and fixed the problem. (My guess the original Datamarine cable was not long enough to get back to the wheel so Oday spliced in a connection). Good luck
