Logo
FULL SITE MENU

transducers not grounded

S

slauder

Regular Contributor
Thinking this is by design. Maybe because the thru hull doesn't expose much metal (any?). Looks funny to have these two inside the boat off the bonding system. I probed it with my sensor when I was checking the other metals. It was not in the -700mv range the way the other healthy ones were. Do I bond them? Does it mess up the sonar readings?
 
??

Threw hull transducers are very sensitive when it comes to placing it in the epoxy (there can be no bubbles) but I do not believe they can be used for anything other than fiberglass hulls. if I understood the question right?
Threw hulls transducers also do not need water contact like external ones do they gain that most often from the water temp wire.
 
Last edited:
Scott; these are bronze thru-hull type 'ducers? I've never bonded them, and never had an issue. I"ve got a pretty big one "B256" in the salt 24/7. Use other stuff not so sensitive for lightning grounds, like shafts, props, and rudders.
 
I asked Airmar about this and they told me it's not necessary to ground the bronze thru-hulls transducers. That's why you don't see an easy way to do it (like a threaded hole). They build something into them so that it's not required (resistor?)

Bob
 
If you are talking about the metal thur-hull styled transducers, you should bond them. They are metal, exposed to the water on the outside of the hull, and are subject to galvanic action. As DD noted, most are a good grade of marine bronze and live in the inert region of the Noble Metals table.

The best method I've found is to get two "extra" threaded nuts, the ones that fit on the inside. Thread them on, after thru-hull installation, so the 'flats' face each other. I used a flat piece of copper stock as a lug between the two nuts. The bond wire is bolted to the corner. Real easy to do before you run the cable; major pain afterwards.
 
DD I have the same (B=Bronze) B256 Airmar in a fairing block... Mark I'm out of the water on blocks and have a very slight drip a couples year now (dont want to discuss the grounding). It was put in with 4200 so I should be able to pull it out.
 
My thought wasn't removing the thru-hull, it was pulling the cable out to put the nuts over the threaded shaft.

If you wanna go down this path, check the continuity between the threaded shaft and the submerged body before you start. I've seen a few that were isolated (electrically).
 
Do you believe if you were to remove a small section of those extra threaded nuts to pass the cable through, that you would still retain enough torque in that " lug sandwich" to maintain continuty and position long term?
 
Now is the time to fix that leak. I also used 4200, but no leaks yet for me! Don't worry with grounding. Do you have the large, hi-speed fairing? Be carefull with those, they are just foam filled. In fact, if it was just an extremely small leak, the risk of breaking the fairing with 4200 may be a factor in the decision. To cut those big ones, a tilt table bandsaw is very helpful.
 
When using a tilt blade or saw; REMEMBER, the angle is opposite the position....ie: if you are cutting a 22 degree angle, insure your proper cutting position before you slice into it....Yup, happened to me so my fairing got mounted on the port side instead of the starboard.
 
Back
Top