Depth gauge intermittently losing its reading

[Meagain]

Hi all
Have a raymarine thro Hull transducer connected to a tridata unit, last year worked fine but since relaunching have noticed at speed it losing its reading ie the depth measurement is static and the word “ depth” keeps flashing. Eventually it resets and measures until losing again. I have noticed by slowing down to displacement speeds , it’s then manages to take a reading.
any thoughts appreciated as I did wonder about connections but if it was this then slowing down to displacement wouldn’t make a differenc. i had the antifouling done for me could this be impacting it? Thanks

 

[Seastoke]

If it’s an old one , like in my old boat it use to sit in oil in the hull when it was low it used to flash

 

[NoviceRod]

I used to have problems with fouling on the transducer, such that later in the season after liftout, the depth reading was lost when planing. I use special Echosounder antifoul, (Marlin Echo Transducer Antifouling | Force 4 Chandlery) which seems to do the trick.

 

[BruceK]

If it’s an old one , like in my old boat it use to sit in oil in the hull when it was low it used to flash

Ditto. Check oil levels

 

[lydiamight]

Meagain has stated that it is "through Hull Transducer" ---not sure if that means a hole through the hull into which the transducer fits or one that sits in an oil filled tube and tranmits the signal through the hull.

 

[PilotWolf]

Getting air under the hull whilst planing will cause loss of signal with most units.

W.

 

[Meagain]

Thanks all, it’s a hole through the hull which the transducer fits into. A 2006 vintage.
the antifoul was what sprung to mind and whether it is impacting the signal. I was told you can pull it out and quickly fit the blanking plug but for clear reason don’t fancy risking that !!

 

[Seastoke]

Thanks all, it’s a hole through the hull which the transducer fits into. A 2006 vintage.
the antifoul was what sprung to mind and whether it is impacting the signal. I was told you can pull it out and quickly fit the blanking plug but for clear reason don’t fancy risking that !!

does the tube stick up say 200 mil in the bilge.

 

[Meagain]

does the tube stick up say 200 mil in the bilge.

pretty sure no, although sitting here not 100% sure

 

[LittleSister]

I was told you can pull it out and quickly fit the blanking plug but for clear reason don’t fancy risking that !!

It's no big deal. You may get a few pints of water in during the process, but probably less. Remove the locking pin(?), unscrew the cap, pull out the transducer (probably easier said than done!), have a hand ready to put over the top of the tube while you're picking up and getting ready the blanking plug, lift your hand and push it in. If all else fails you can push the transducer back in.

 

[vas]

haven't done that remove/plug thing on my AIRMAR transducer, hindsight is a wonderful thing should have placed it in a more accessible spot...
However, it's not 200mm protrusion, more like 100, and note that most of them go in only one way and there's usually an arrow pointing the bow (especially the 3ducers).
Just saying as if you're in a hurry trying to do the move with water splashing in, you may panic a bit and try it the wrong way around and freak out more
Mind in the med, speed wheel only manages to work for 2weeks at most, depth/temp is always fine no matter fouling.

 

[LittleSister]

. . . note that most of them go in only one way and there's usually an arrow pointing the bow (especially the 3ducers).
Just saying as if you're in a hurry trying to do the move with water splashing in, you may panic a bit and try it the wrong way around and freak out more

As I recall it's only the last 1/2" or less of pushing the transducer in where the direction has to be correct, in order to locate the tabs on the top of the transducer in the slots in the housing (or is it vice versa?) which ensure the paddle-wheel is correctly orientated. That is, you will have transducer over 3/4 of the way in, and no water coming in, before you have to worry about turning it to the correct direction.

Which reminds me, handy tip - don't forget to thread the locking ring, if you've previously removed it, on to the transducer and its signal wires before you put the transducer back in the housing. (How do I know that? )

A bit of grease on the transducer and blanking plug sealing O rings helps. You can buy service kits for the transducer which include replacement O rings.

Having said all that, I suspect fouling ahead of, or around, the transducer is more likely than on the transducer itself, but despite the OP's fears this is an easy job (if you can get the transducer out!) to eliminate one possibility.