Airmar ST 800 Odd Problem

Marc14857

Marc14857

.
Jun 5, 2004
485
Hunter 44 Mystic, Ct
Haven’t been posting on this forum for awhile ever since selling my Hunter but I am having an odd issue with my speed transducer on my current boat and hoping someone can help… My ST 800 Speed transducer stopped working. I pulled the transducer from inside the boat, cleaned it up and spun the paddle wheel easily by hand and did get a reading at my ST 60 display. I reinstalled the transducer, lining up the key with the notch on the housing. The knot meter would only read “000” regardless of the boat speed. I went through this process several times with no success. I even hired a diver to clean the bottom just in the off case something was blocking water flow across the paddle wheel. This did not help either.
I am getting ready to replace the transducer this winter but wanted to ask if anyone had any ideas beforehand.

TIA
Marc
S/V Surprise
 
D

dlochner

.
Jan 11, 2014
13,030
Sabre 362 113 Fair Haven, NY
Sounds like there might be fault in the cable or connector. When the transducer is installed the wire is moved and it breaks the circuit.
 
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Likes: ggrizzard
kappykaplan

kappykaplan

.
May 1, 2011
5,050
Pearson 37 Lusby MD
Marc14857 said:
I pulled the transducer from inside the boat, cleaned it up and spun the paddle wheel easily by hand and did get a reading at my ST 60 display.
Click to expand
Is the transducer installed in the through hull correctly? My transducer has arrows that must be aligned to point at the bow.
 
S

sesmith

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Jul 1, 2010
990
Catalina 350 Port Huron
You should definitely see a reading if you spin it by hand. You could test it at the gauge unit using a scope or a multimeter set to ac, assuming it's one of the older analog units. That's about all the troubleshooting you can do other than what you've already done. If you order a new one, you may want to call Airmar direct to get the right part #. You may also have to change out the thru-hull. Did this on my Catalina 350 this spring. Luckily the new thru- hull was the same diameter as the old one, but I did have to swap it out to get the new transducer to fit.

Edit, misread your original post. If you got a reading when spinning it by hand, then the wiring and head unit are probably ok. I had a similar issue with mine. The failure was intermittent. I could spin it by hand and it almost always would work fine. Put it in the water, and it would stop working a half mile into a trip, if it worked at all. Mine also has the temp sensor in it and I noticed it would quit working after it had been in the water a few minutes. I figured it was water intrusion into the transducer. New transducer fixed both problems.
 
Last edited:
Marc14857

Marc14857

.
Jun 5, 2004
485
Hunter 44 Mystic, Ct
sesmith said:
You should definitely see a reading if you spin it by hand. You could test it at the gauge unit using a scope or a multimeter set to ac, assuming it's one of the older analog units. That's about all the troubleshooting you can do other than what you've already done. If you order a new one, you may want to call Airmar direct to get the right part #. You may also have to change out the thru-hull. Did this on my Catalina 350 this spring. Luckily the new thru- hull was the same diameter as the old one, but I did have to swap it out to get the new transducer to fit.

Edit, misread your original post. If you got a reading when spinning it by hand, then the wiring and head unit are probably ok. I had a similar issue with mine. The failure was intermittent. I could spin it by hand and it almost always would work fine. Put it in the water, and it would stop working a half mile into a trip, if it worked at all. Mine also has the temp sensor in it and I noticed it would quit working after it had been in the water a few minutes. I figured it was water intrusion into the transducer. New transducer fixed both problems.
Click to expand
Im thinking transducer as well. Temp sensor seems to be working all of the time. Going to take one more look for any obvious wiring issues at the head of the transducer and if i cant get it to work, will order a new transducer.

Thanks
 
S

steven685

.
Jan 22, 2008
33
Ericson 29 tall rig old orchard beach, maine
Marc14857 said:
Haven’t been posting on this forum for awhile ever since selling my Hunter but I am having an odd issue with my speed transducer on my current boat and hoping someone can help… My ST 800 Speed transducer stopped working. I pulled the transducer from inside the boat, cleaned it up and spun the paddle wheel easily by hand and did get a reading at my ST 60 display. I reinstalled the transducer, lining up the key with the notch on the housing. The knot meter would only read “000” regardless of the boat speed. I went through this process several times with no success. I even hired a diver to clean the bottom just in the off case something was blocking water flow across the paddle wheel. This did not help either.
I am getting ready to replace the transducer this winter but wanted to ask if anyone had any ideas beforehand.

TIA
Marc
S/V Surprise
Click to expand
I have a st 800 in my Catalina 30. I have found that where I located it next to the Keel sometimes it will blink off. What I mean is it will give me a false reading on depth when I heel. When I come straight up it does not come back. It takes a few moments or even minutes for it to register correctly. I have tried all the things you suggested. But I live with it. I have not contacted Garmin or Airmar but that is a great idea! I just thought it was not wide enough angle to register when heeling.
 
TimFromLI

TimFromLI

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Jan 7, 2014
451
Beneteau 45F5 51551 Port Jefferson
I had a similar problem once, the transducer was installed incorrectly. It was not pushed all the way in.
 
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