I thought I should share my experience fixing ST-60 depth instrument. The reason for this is that the failure was a result of a design flaw on my Hunter 33 2006 and also that it is not easy to troubleshoot. Also, you will see from my post that it is likely to happen on other boats.
It took me quite some time (several months) to figure out what was wrong. In the end I found that the steering mechanism was pinching the transducer cables in the space under the steering column near the place where they enter the pedestal tube going to the instrument displays. The failure was gradual, the depth sounder stopped displaying the correct depth now and then, for increasingly longer periods of time; the display showed LAST dept instead, until it caught up with measurement. First I thought that I got some algi or trapped air on the transducer. Ultimately it stopped working altogether and I thought that the transducer gradually failed, but that was not the case. When I finally got to trace the cable from the transducer to the display I found that it was partially cut under the steering column. At the same time I found that three more cables were damaged in the same place: the speed transducer cable was completely cut (it never worked since I bought the boat, but I didn't care as I got the speed from GPS/chart-plotter), a cable which seems to be powering the instruments (yellow, red and bare wires) had damaged the outside insulation but the individual wires were OK, and another cable completely cut but I found it was not connected to anything in the instrument console.
Anyway, I found the wires were being pinched between the pedestal output lever and the stop block that limits how far the wheel can turn. This gradually chewed the cables. I was able to pull down the cables down through the tube from the console. This was a two-person job: one pulling from under the pedestal and the other pushing the cable into the tube's side opening inside the console. There is plenty of spare length of the cable inside there, so the only problem is to figure out which cable is which. The speed and depth transducer cables are clearly marked as such by a text printed on the insulation, so this makes it easier. Also the two transducer cables have different number and colour of wires inside. The work requires removal of the aft part of the cockpit floor and dexterity of the person pulling the wires under the pedestal, not to talk about awkward lying position.
Ultimately, I pulled the wires enough to be able to reconnect them, solder them together and insulate them individually as well as the whole reconnected part of the cable using heat shrink tubing. Once I got the cables back in place and away from the steering mechanism, I made sure they cannot move out of place by wedging them in with a piece of hard insulation foam I had handy. For good measure I fixed that piece of foam with some Gorilla glue. I am attaching a page from the manual to show relevant parts of the steering mechanism
After the work was done both the speed and the depth instruments are working fine.
I wish the engineers designing the boat had secured the cables better.
It took me quite some time (several months) to figure out what was wrong. In the end I found that the steering mechanism was pinching the transducer cables in the space under the steering column near the place where they enter the pedestal tube going to the instrument displays. The failure was gradual, the depth sounder stopped displaying the correct depth now and then, for increasingly longer periods of time; the display showed LAST dept instead, until it caught up with measurement. First I thought that I got some algi or trapped air on the transducer. Ultimately it stopped working altogether and I thought that the transducer gradually failed, but that was not the case. When I finally got to trace the cable from the transducer to the display I found that it was partially cut under the steering column. At the same time I found that three more cables were damaged in the same place: the speed transducer cable was completely cut (it never worked since I bought the boat, but I didn't care as I got the speed from GPS/chart-plotter), a cable which seems to be powering the instruments (yellow, red and bare wires) had damaged the outside insulation but the individual wires were OK, and another cable completely cut but I found it was not connected to anything in the instrument console.
Anyway, I found the wires were being pinched between the pedestal output lever and the stop block that limits how far the wheel can turn. This gradually chewed the cables. I was able to pull down the cables down through the tube from the console. This was a two-person job: one pulling from under the pedestal and the other pushing the cable into the tube's side opening inside the console. There is plenty of spare length of the cable inside there, so the only problem is to figure out which cable is which. The speed and depth transducer cables are clearly marked as such by a text printed on the insulation, so this makes it easier. Also the two transducer cables have different number and colour of wires inside. The work requires removal of the aft part of the cockpit floor and dexterity of the person pulling the wires under the pedestal, not to talk about awkward lying position.
Ultimately, I pulled the wires enough to be able to reconnect them, solder them together and insulate them individually as well as the whole reconnected part of the cable using heat shrink tubing. Once I got the cables back in place and away from the steering mechanism, I made sure they cannot move out of place by wedging them in with a piece of hard insulation foam I had handy. For good measure I fixed that piece of foam with some Gorilla glue. I am attaching a page from the manual to show relevant parts of the steering mechanism
After the work was done both the speed and the depth instruments are working fine.
I wish the engineers designing the boat had secured the cables better.
hose was only held on by friction and only with 1/4" holding it at that. Construction screw-ups happen. Again, I suggest this was a construction problem.