ST60 Depth Issue

[NeilB]

Recently removed a RL70C and replaced it with a C120MFD. Employed a qualified technician to install and run all necessary wiring. Connected new (used) C120 to my existing ST60 Wind, Speed & Depth, and ST6001+ Auto Pilot with SG1 Controller Computer. I had the tech connect the old RL70C at Nav station as a slave.
The problem is after the install, about 1 1/2 hours into each cruise trip,
the ST60 Depth starts doubling and tripling the depth. After maybe 30 minutes or less, it either shows ------ across or freezes with "last depth" which was incorrect anyway. After being turned off overnight it starts out each morning working properly until underway 1 1/2 to 2 hours and it will then register 99 in 25 ft or 38 in 17. All over the place. I tried leaving it on just sitting in marina and sure
enough about 1 1/2 hours of being on it went from 2 ft which was correct as it was low tide in the marina to 17, 18, 20.
Any suggestions as to possible problem, Wiring? Computer issue?
I am at a loss. If it matters, it is a 2004 Catalina 36MKII.
Thanks!
NeilB

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Neil,

Proper operation of Raymarine depth sounding products require that depth of the water beneath the transducer be at least 3'. When operating in depths less than this value, the depth sounding product may report 2 to 3 times higher depth values (due to a second or third reflection of the the sonar ping from the water's surface) or may report -.- for the reported depth. While some may report operation in depths which are slightly less than this value, operators should not expect their depth sounding products to report a depth value when the depth of the water beneath the transducer is less than 3'. Bottom loss within a vessel subject to large heel angles (ex. a sailing vessel), may also occur when operating with a heel angle when sailing in deeper water.

Should the problem occur when the vessel is located in depth between 3' to 120' beneath the transducer and the vessel not be subject to heel a the time that bottom loss occurs, then it would be recommended that the depth instrument be tested with another transducer which has been suspended over the side of the hull. Should the problem persist using the test transducer, then the ST60 Depth instrument should be replaced (recommend replacing with an i50 Depth instrument), as Raymarine can no longer service ST60 instruments.

[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?

[Chuck - Raymarine - Moderator]

Neil,

Thanks for the clarification concerning the depth of the water and the offset. The offset must be applied in the instrument, not within the MFD's settings. Can you further explain your comment about "piggy back"? Are you referring to how the MFD is being powered or how the MFD has been interfaced to the SeaTalk bus? Also, when interfacing the MFD to a SeaTalk bus, it is recommended that the red lead of the SeaTalk cable connecting the MFD to the SeaTalk bus be severed and that the severed red leads then be insulated to prevent shorting.

[NeilB]

Thanks, The MFD is powered direct to the panel and is piggy backed to
the course computer. I am on my way to check out the red lead and will get back to you.
Neil

[Chuck - Raymarine - Moderator]

Neil,

It is indeed acceptable to interface the MFD's SeaTalk cable to one of the SeaTalk ports of the S1G Autopilot Course computer. As recommended previously, it is recommended that the red lead of its SeaTalk cable not be connected to the red SeaTalk terminal of the S1G. This is more for housekeeping, and I don't believe that it would be responsible for the reported issue. It is recommended that the aforementioned troubleshooting be performed to isolate the problem to the depth instrument or transducer.

One last note, if an in-hull instrument depth transducer (i.e. P79) has been installed, then it is recommended that the fluid level within its reservoir be checked to ensure that it is full. The P79 must be fully immersed in fluid to perform properly.

[NeilB]

Attached is picture of wiring; Also I will check fluid on transducer. I am of the opinion that on the Catalina36MKII, the transducer is fully encapsulated.

[Chuck - Raymarine - Moderator]

Neil,

Unfortunately, the resolution of your photo was too low be magnified without blurring the image. That said, one would have to trace the SeaTalk cables exiting the course computer's SeaTalk terminals to know what they had been connected to. Should you be able to do so, then simply disconnect the red lead of the SeaTalk cable connecting the MFD's SeaTalk port to the autopilot course computer's red SeaTalk terminal.

[NeilB]

Just trying one more view in case it is clearer.

[Chuck - Raymarine - Moderator]

Neil,

While not common, is certainly possible and acceptable to insert the leads from more than one SeaTalk Cable into the set of terminals of one of the autopilot course computer's SeaTalk ports. Unless the installer had labeled each of the SeaTalk cables, there would be no way to identify what devices these cables had been connected to. Per my prior response, one would have to trace the SeaTalk cables exiting the course computer's SeaTalk terminals to determine what they had been connected to. Should you be able to do so, then simply disconnect the red lead of the SeaTalk cable connecting the MFD's SeaTalk port to the autopilot course computer's red SeaTalk terminal.