Navman Depth Sounder Transducer

[aquazul]

I have a Navman Depth 3100 on my Azuli F40 Cat (Foam sandwich hull).
The transducer is mounted in-hull at a solid f/glass section near seawater intake.

The sounder has worked OK for about 11.5 years.
But recently the display started showing "- -" instead of the depth numbers.

I read that you could check that the sounder was sending a pulse to the transducer by using an old AM radio tuned to 200KHz and listen for a clicking sound to confirm that the sounder was sending the ultrasonic pulse.

I did this test and it worked. I could hear a clicking sound through the radio, when the sounder was powered on, the clicking would stop when I turned power off to the sounder.

Then I removed the transducer from the hull and put it in a bucket of water. The display started showing a reading. From this I assumed the transducer may be OK, but the interface to the full had been compromised somehow.

So then I cleaned up the transducer surface and the hull surface and reattached with SikaFlex.

Now it is just showing "- -" again.

Has anyone else had this experience?
Can anyone suggest another test to confirm the transducer is OK or not?

[irwin37]

I have found silicon works best for this, short of making a box to fill with mineral oil. Make sure there are no air bubbles when setting the transducer. Did you mention you have a cored hull, if so you may have problem getting a signal to go through the hull.

[gathhill]

Originally Posted by irwin37

I have found silicon works best for this, short of making a box to fill with mineral oil. Make sure there are no air bubbles when setting the transducer. Did you mention you have a cored hull, if so you may have problem getting a signal to go through the hull.

The op stated the hull is sandwiched but transducer is mounted in a solid fg section of the hull. He also stated it's been working fine for 11 1/2 years. Since you have found silicone worked best for you, I'm assuming you've installed more than one. where did you install your through the hull transducer and what type do you have? Curious, because I have issues with this type also.

[DeepFrz]

Maybe a bad wiring connection back to the instruments? Check all your wiring that you would have moved when running your bucket test. I suppose there is a possibility that the signal is so weak the receiver isn't picking up the sound from more than a few feet depth.

[gathhill]

One test to determine if its the transducer or the head would be to put the transducer over the side to determine if it's reading or not. If you get a reading it's a problem shooting thru the hull if not it has to be between the transducer and the read out. Mine is a solid glass hull and I can't get a reading thru it but hanging over the side of the boat it works fine.

[irwin37]

The hull will definitely attenuate the signal, I have had to silicon a transducer to the inside of my hull this year as the thru hull gave up on me. Purchased a cheap puck transducer, Cut 4" PVC pipe to the hull angle and about 3- 4 inches high, put some modeling clay on the bottom edge and pressed to hull. Fill with water and place transducer in the water to see if I get a good signal. Moved the pipe around to a few places until I found the best spot. Cleaned hull, wipe with MEK, made a pyramid of silicon on both the hull and transducer. Turn the transducer as you press it to the hull. You want to squease most of the silicon out slowly to avoid making air bubbles and make the silicon layer fairly thin. (less attenuation), Yes I have done this many times on customers boats for quick repairs or where the customer does not want a thru hull fitting, Work well but thru Hull is better.

[aquazul]

Thanks for replies and suggestions guys.

Just tried putting the transducer in the water over the side of the boat and it works fine. But still not working through the hull.

Either something has made the hull attenuate the signal more than before, or the signal is not as strong as before. Not sure what could make it suddenly stop working after 11 1/2 years.

Seems my choices are to by a new sounder or put the transducer through the hull.

[GordMay]

Greetings and welcome aboard the CF, aquazul.

Transducers that are between 10 and 20 years old should still work well enough, but will probably produce less energy than when they were new. Accordingly, it may work in direct contact with water, but not when partially “masked” by hull material.

[gathhill]

Aquazul, my depth sounder is brand new and does same as yours. Best choice would be thru hull if she's on the hard now or will be. My next attempt will be what"irwin37" did with the 4"pvc pipe. Hit or miss I guess.

[Jim Cate]

Only a small chance, but have you checked for a buildup of growth on the hull in the area where you mount the transducer?

Jim