ST60 Depth Issue

[NeilB]

Thank you for your reply. Yesterday I turned electronics on sitting in marina at high tide and it took approx. 1.5 hrs, it started jumping 25, 3, 18 all over the place. Seems it has to warm up to misbehave. I will try and test as you suggest or replace the ST60. Just wanted to double check as it never happened until the C120 was installed. I have the Depth offset 5.5 ft, so the reading is always the water beneath the keel. Previous to install of the C120 and traveling the ICW the Depth would read correct as far as we knew, sometimes in the sketchy shallow areas as -5 ft. The first time we noticed a problem was in the St Helena sound in March. Showing 95' but the boat traveling with us showed 25'. We shut everything off and it would correct, but now it has to be shut off over night and then takes couple hours running the ICW to act up. Before I purchased new, just wanted to make sure it couldn't be a miss wiring from the install of the C120. Does seem it has to heat up to act up.

Also in checking and double checking the wiring, I noticed the installer piggy backed the C120. Could it be too much? Maybe need to use a block?