Speed Transducer Works on the hard but not in the water

[pbyrne]

Last season I had no speed and therefor no true wind either.  We sail on a river with steady current, so it is useful to see what the current is relative to SOG.

-Boat is in fresh water
-Paddle wheel spins freely making a fun 'zing'! sound, paddle wheel shaft looks good
-Able to get speed to indicate on instrument with someone spinning the paddle wheel
-Pulled speed transducer and found a split O ring at the base closest to the paddle wheel
-Transducer showed signs of dampness on body as shown in photo

From other reading I've done on this topic the transducer may not be a sealed unit and the failed O ring allows fresh water to get into the transducer and short it out when the boat is in the water.

Assuming this is correct, what is the best approach to correct this?

I'm assuming I should dry out the transducer, possibly spray it with some kind of hydrophobic solution to clear out the water trapped in it (WD 40?) and replace the O ring, re lube the O ring seals (3 of them on the transducer) and reinstall.

Is it possible to get a new O ring or am I stuck with having to purchase a whole new transducer..?

Considering how questionable the design of this unit is with 1 O ring between the outside and the internals of the transducer I'm hoping there are readily available parts!

[Jim Hardesty]

Is it possible to get a new O ring or am I stuck with having to purchase a whole new transducer..?

You can get O rings at any good hardware or autoparts store.  Best to bring in the old O ring and match it, then record the size.  Cost is pocket change, buy a spare.  I would try drying in rice, like a wet cell phone.  Is the paddle wheel in the correct direction?  That is with the cup side forward.  On Shamrock there's a notch and tab to position the transducer forward, it's small and care in needed when putting the transducer back in.  FWIW  Once a season I need to pull the transducer in the water to clean the paddle wheel.  Nervous first time but after a few times never had much water come in.
Hope this helps,
Jim

[waughoo]

I would consider getting a replacement paddle wheel kit.  Despite how clean it appears, there might be just enough build up of schmutz on the paddle wheel and pin that it doesnt work in the water.  I just did mine yesterday and the kit I bought came with the wheel, pin and a stack of orings.

[Jim Hardesty]

By the last picture, looks like a lot more side clearance than on mine.  Perhaps a PO changed to wrong paddle wheel.
I've considered a new paddle wheel.  But don't have a decent local source to take it into and match it.  Do all C34's take the same?  Anyone know the part number and a good source?
Jim

[pbyrne]

Interesting!  Can you provide the kit info to order?

It really spins very easily though.  You can blow on it and it turns.

I would consider getting a replacement paddle wheel kit.  Despite how clean it appears, there might be just enough build up of schmutz on the paddle wheel and pin that it doesnt work in the water.  I just did mine yesterday and the kit I bought came with the wheel, pin and a stack of orings.

[pbyrne]

I've corrected the photo.  It still suffers from 'selfie nose' as the cool kids call it.  It makes the gap look bigger than it is!

I'm the second owner of the boat, and PO wasn't the type to mess with things.  I'm pretty sure it's OEM.

As for whether all C34's take the same I'd say they do insofar that this transducer was the one in supply at the time.  At some point there must have been different types.  I'm not that versed on the electronics side yet (working on it), so I'm not sure if this transducer would be considered as part of the Raymarine ST60 suite or not.  Meaning, when the Raymarine tech changed at some point the transducers might have as well.

By the last picture, looks like a lot more side clearance than on mine.  Perhaps a PO changed to wrong paddle wheel.
I've considered a new paddle wheel.  But don't have a decent local source to take it into and match it.  Do all C34's take the same?  Anyone know the part number and a good source?
Jim

[wingman]

I've got the same problem. I believe mine is an Airmar DST 800, definitely not OEM.

I am lusting after the digital unit (UDST800) that doesn't have a paddle wheel, but at $1000 not in my future.

[waughoo]

Honestly, i just googled for raymarine transducer rebuild kit.  I thin West Marine had them in stock at a reasonable price (gasp!!) So i just ordered it.  I will have to look next time i am at the boat to see if there is a part number on the bag it came in.

[Gary Brockman]

Airmar provides transducers for the majority of marine electronic companies. You can easily get replacement kits online from many sources. You need to know which model you have, such as a triducer vs just speed, as there are different kits for each. Heres a link to see the available kits: https://www.bluebottlemarine.com/categories/airmar-transducers/transducer-parts/paddle-wheel.html

When I replaced mine last year when the speedo would work sometimes and not others. It work work perfectly when out of the water and only intermittently when in the water. Airmar told me it was probably the pin. They also told me that the paddlewheel bearing should be replaced every 5 years.

[Dave Spencer]

pbyrne,
Gary is right about Airmar.  They provided most transducers.  Here's an Airmar cross reference guide:
https://airmar.com/xref.html
Based on the picture of your display, it looks like a Raymarine ST60 system.  The Raymarine pn for the speed transducer is almost certainly E26031 which is an ST800/P120 transducer. 
Binnacle in Halifax has the service kit here:
https://ca.binnacle.com/p11632/Raymarine-Paddle-Wheel-Kit-for-Retractable-Speed-D234/product_info.html
The whole transducer is now on sale at Binnacle for an excellent price but there is significant pain running the cable to the helm.  I don't think splicing is recommended but I've done it.  https://ca.binnacle.com/Electronics-Transducers/c12_565/p7221/Raymarine-Speed-Temperature-Transducer-E26031/product_info.html
The Chandlery in Ottawa might have these items or can get them for you.  https://www.thechandleryonline.com

[Ron Hill]

pby : I'd cleanup that paddle wheel and then I spray anti fouling paint on mine. I don't think that the space on the sides make any difference unless it is installed in the hull where the contour of the hull causes the wheel to ride on the side.

Also make sure it is installed properly - so the flat of the paddle wheel is forward!!

A few thoughts

[Roc]

Your picture with the red arrow...  you see those ribs on the transducer.  Well right above those ribs is where two parts of the transducer snap together.  You can see the line.  It comes in two parts.  Those two parts create the electrical connection to the paddle wheel.  When the transducer is dry, there is no issue with the paddle wheel to send the pulse through.  But when it's wet, there probably is a short, and the electrical connection between those two parts is compromised.  Try sticking it in a bucket of water for a while and then see if it works.  I think water is getting into that section that is snapped together.

[ghebbns]

I had a similar problem.  When on the hard, I could spin the wheel and it would register.  When in the water, if I removed the transducer and spun the wheel, it would register.  But underway, I got nothing.
Turns out the hole on the paddlewheel (not sure the technical name) was worn enough that when in the water, the wheel floated up enough for the paddles to catch on the hull of the boat.  When on the hard, gravity allowed the wheel to stay down enough to clear the hull.  Replacing the paddlewheel solved the problem.

[pbyrne]

Ah! Perhaps that's why they suggest a 5 year fresh water replacement schedule!

Very good to know, thank you, I'll check for that.

I had a similar problem.  When on the hard, I could spin the wheel and it would register.  When in the water, if I removed the transducer and spun the wheel, it would register.  But underway, I got nothing.
Turns out the hole on the paddlewheel (not sure the technical name) was worn enough that when in the water, the wheel floated up enough for the paddles to catch on the hull of the boat.  When on the hard, gravity allowed the wheel to stay down enough to clear the hull.  Replacing the paddlewheel solved the problem.

[pbyrne]

Yes this is my suspicion as well.  I'll try to dry it out as best I can with rice as suggested and replace the O ring.  It does seem to function on the hard, and no exposure to salt water so it's worth try to get it working this season.  We have to haul out every year so worst case I go without again and rely on the chartplotter GPS for a few months; and then replace the whole unit.

It's a poor design in my opinion.  It seems to need to be kept dry, yet you have to remove it to clean it, and then reinstall as water is pouring into the boat which guarantees there will be water still in the thru hull the transducer is mounted in.  Makes no sense.

BTW does anyone know what the lubricant for the O rings should be?

Your picture with the red arrow...  you see those ribs on the transducer.  Well right above those ribs is where two parts of the transducer snap together.  You can see the line.  It comes in two parts.  Those two parts create the electrical connection to the paddle wheel.  When the transducer is dry, there is no issue with the paddle wheel to send the pulse through.  But when it's wet, there probably is a short, and the electrical connection between those two parts is compromised.  Try sticking it in a bucket of water for a while and then see if it works.  I think water is getting into that section that is snapped together.