Depth Sounder questionI have a...

[Captain_Jeff]

Depth Sounder question

I have a 2007 Sundancer 300.  The depth sounder seems to work intermittently now.  It has a through hull transducer.  Any ideas as to what would cause it to work intermittently?  I'm hoping not to have to replace the transdoucer.

[wingless]

My assumption is that this had previously worked fine, now something has changed making this problematic.

Start w/ the basics.

Has anything changed, like a new 1.21 Jigawatt stereo or other electronics added between working fine and having issues?

Monitor the voltage supplying power to the instrument, including during the problem. At the instrument measure +12V to ground. It should be reasonably constant.

Do a light tug test on the transducer connections to verify solid retention. Disconnect the transducer and perform a visual inspection of the transducer wires. Verify that all wire strands are intact and not corroded.

Do a visual inspection of the cable over the entire length. Verify that the cable is not cut, crushed or kinked.

The cable should be at least 1m from VHF + SSB cables. The cable should be at least 2m from the ±20² radar beam.

Has the surface of the transducer been verified to be free of marine growth or other damage? Mine may be removed from the engine room and replaced w/ a dummy plug. I use the two hand method, to yank / replace w/ one hand while covering / exposing the hole near the keel w/ the other hand.

[Captain_Jeff]

Thank you for the reply Wingless. Much appreciated. The surface of the transducer is clean. It started acting up a couple of years ago but seems more frequent now. I have looked at the wire but it disappears into the top of the transducer so I'm not sure how to check the connection. I'll look at it a little closer.

[wingless]

Glad to help.

The transducer end of the wire is potted. It cannot be removed or inspected.

The instrument end of the wire must be inspected.

[Captain_Jeff]

Ah! Ok, will do that.
There is an extra transducer attached to the one that's in the hull. No wires coming out of the extra one though. I assumed the wire would be taken out of the one and added to the other. I guess that's not the case?

Jeff

[wingless]

That "extra transducer" is probably the dummy plug.

My guess is they are coupled together by large rings?

On mine, I decoupled those large rings so the transducer and the dummy plug may be handled separately. I find that the best way to do the swap from transducer to dummy plug, described above.

[wingless]

Any luck / update?

[Captain_Jeff]

Thanks for following up!
I actually haven't been back to the boat since our last correspondence. Unfortunately, I've been out of town. I hope to get there tonight and will check connections.
Jeff

[Captain_Jeff]

Hey Wingless, last night I followed the wire back from the transducer. Noticed that it was right against the exhaust riser and had worn right through the rubber sheathing. There was still a thin covering of some sort over the wire itself, but I'm thinking that probably wasn't enough insulation. I've wrapped it now. It's working, so I'll see if that fixed it and it continues to work.

[wingless]

Thanks for the update.

If the repair remains flakey, then there are alternative repair methods that could provide a more robust solution.

The appropriate repair method would be selected based on the cable construction. A shielded cable needs a different method than an unshielded cable.

Please report if issues persist.

[JRT]

Just FYI, I have a 300DA with 350 magnums and i had a similar problem with my thru hull depth finder at speed. It was finally resolved to be bubbles from the thru hull rim going across the face of the transducer.. The manufacturer told me it wasn't supposed to work above about 30MPH . I installed an aftermarket depth indicator with a stern mount transducer, works at all speeds and has many more features than the factory unit.

[Captain_Jeff]

Thanks JRT! I thought I had fixed the problem when I found the bare wire. It happened again after though. I swam under the boat and gave it a good cleaning. No problems since. It seems to be very sensitive and if there is even a thin layer of film on it, it acts up.