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What's going on with my transducer

Old 04-30-2018, 07:23 AM
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Default What's going on with my transducer

This was installed new about 5 years ago, in Spring of 2013. Was underneath the boat yesterday and noticed this corrosion and part of the bottom of the transducer pulling away in one spot. Should this be happening after 5 years? This is a Garmin transducer for the Garmin GPSmap 740s. There is corrosion all around it, but you can see the one spot that is peeling a little bit also.


Old 04-30-2018, 02:35 PM
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Nope. Didn't really use anything on it. I tried to keep any of the bottom paint away from it, but made the mistake of not telling my son one year when he painted it, he was 8 and didn't know to stay away, he was going around it with a roller. Luckily he only got around the edges, as you can see, he was smart enough not to coat the actual transducer face. You can see the white all around it, that area doesn't get any paint when we paint the bottom in the Spring.
Old 05-01-2018, 07:27 AM
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Does regular bottom paint being on the metal ring around the transducer face promote galvanic corrosion, same as if regular bottom paint in used on trim tabs, engine bracket or outdrive?

I always figured as much which is the reason I never put any paint near it, except for the time my son got some around the edges of it, but that was 3 or 4 years ago.

Also can transducer paint go right over the face of the transducer or is it just safe to coat around the ring of it, similar to an outdrive paint being safe for an outdrive?
Old 05-01-2018, 09:14 AM
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Originally Posted by Southbay View Post
Does regular bottom paint being on the metal ring around the transducer face promote galvanic corrosion, same as if regular bottom paint in used on trim tabs, engine bracket or outdrive?

I always figured as much which is the reason I never put any paint near it, except for the time my son got some around the edges of it, but that was 3 or 4 years ago.

Also can transducer paint go right over the face of the transducer or is it just safe to coat around the ring of it, similar to an outdrive paint being safe for an outdrive?
It looks like galvanic or electrolytic corrosion, not fouling. I always thought (maybe wrongly) that bottom and transducer paint just protect against biological fouling. There are all sorts of weird circulating currents and electrical potential gaps underneath a boat while running; you may want to check the condition of your anodes and also the transducer wiring to make sure its properly grounded. It definitely looks like something electrical is going on around the transducer.
Old 05-01-2018, 09:34 AM
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Originally Posted by Auburn1 View Post
It looks like galvanic or electrolytic corrosion, not fouling. I always thought (maybe wrongly) that bottom and transducer paint just protect against biological fouling. There are all sorts of weird circulating currents and electrical potential gaps underneath a boat while running; you may want to check the condition of your anodes and also the transducer wiring to make sure its properly grounded. It definitely looks like something electrical is going on around the transducer.
Yeah, pretty much what I was thinking too. Why I asked about the bottom paint, although it's barely on there and hasn't gotten any on it in years. I also see that transducer paint contains 25% cuprous oxide, same as bottom paint, just doesn't have the solvents that would damage the face, so I guess the bottom paint having gotten on it isn't the cause. Zincs are good, no other galvanic issues anywhere on the boat.

I'll check the ground on the transducer and hit it with some MDR.

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