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      I was sceptical when I found this fix on the Internet but after months of intermittent log performance with my (original to the boat) Raymarine ST60 log all is now well.

      The log has not been reliable for ages. I did try removing the transponder (with lots of water to clear up) but that seemed fine, so I became suspicious.

      I had noticed since I bought the boat that the sea temperature reading was ridiculous. I had also noticed that sometimes (a) the log seemed to work fine, or (b) the reading was just 0.00 or, more worryingly, (c) the reading was 3 dashes -.–. I suspected a loose connection at the instrument in the binnacle but didn’t want to disturb the seal between the instrument panel and binnacle as I had spent a lot of time getting that watertight after discovering that leaks there were causing water to reach the aft cabin.

      I found on the net that the ST60 speed transponder also includes a thermistor to detect sea temperature and that these are very prone to failure. When they fail, they cause the instrument at the binnacle to think it is a slave, not a master, so it goes into slave mode and won’t show the speed correctly (or not at all).

      The solution is incredibly simple and I achieved it without disturbing the instrument panel. I broke into the black plastic sleeving on the cable coming from the speed transponder (there was lots of spare neatly folded and clipped to the bulkhead near to the depth and speed transponders) and identified the BROWN and WHITE wires, which are the wires from the thermistor. I cut these wires, leaving the other wires continuous, and soldered a 10k-ohm resistor between them. The log read-out now works perfectly. The temperature read-out is now fixed at 22.0 degrees, but I ignore that anyway.

      I had come close to a major investment in a new transponder, which would then have meant a lot of pulling-through of the new wire and disturbance of the binnacle instrument panel. And all to keep a 14-year-old ST60 instrument going. I considered also a whole new instrument.

      Very happy with the result. Cost – a few pence for the resistor.


      Thanks for posting that Jonathan

      My log has been tempremental for about 5 years now, and I got to the point of taking the transponder out and giving up with it. I’ll certainly try your fix now.

      I bet there are loads of boats out there with this problem, and people buying new when they don’t need to.

      Good work, and thanks.



        Nice post good info!!!!

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