This has everybody stumped!

[LeeV]

The Situation: On our new-to-us C-36 there are 2 transducers under the forward berth. The one stbd of center is depth (working) and has a blank laying beside it. The other to port is the SOG, but is laying to the side with the blank plugging the thru hull.
Instruments: Nexus instrument cluster (wind, speed, depth), Raymarine C80 mfd chartplotter, gps, radar


1st Action: The only reason I could think of for the SOG transducer to be out of its slot is the paddle wheel, so I checked it, and lo and behold, it was stuck. I cleaned it up and got it to the point where I could blow on it and it would spin freely. Awesome; I solved the issue! Uh, not quite.....


Installation: I pulled the blank and quickly inserted the transducer. Oh %#@! The transducer has a much smaller diameter than the hole. What the *&^%? Hurriedly replaced blank. Bailed water. Pulled again (idiotic, but I just couldn't believe it!) with same results - definition of insanity.


I have a gps so I'm not worried about finding my SOG, BUT, I'd like to put everything back as it was, and this one makes no sense. The PO can't recall, and the question leaves everybody scratching their heads!



Any ideas???!


Thanks,

[Cheechako]

Well... it sounds like the wrong unit... or...Is the Oring on it? Paddle wheels gum up a lot, some people leave them out until they need to use it.

[LeeV]

I've cleaned it and it works like a charm. Seems to be the correct unit and all the original wiring but the diam of the transduced definitely doesn't match that of the through hull, and it looks like there were never any repairs.

It's almost as if the transducer is missing a sleeve or something, but I've never heard of that nor seen one in my research.

Odd, to say the least.

[boatpoker]

Not sure I'd be playing mix'n'match with pieces securing a hole in the bottom of my boat.

[dlymn]

get out the micrometer and calculate diameter difference. you might be able to get a larger o ring to make up the gap. leave the current oring in place and slide the new one on from the bottom of the unit You might need some sealant between them. you should put another ring at the top to keep the unit straight. BUT what is going to hold the unit positively in place? will iit screw into a fitting? I don't much like a push fit as the only thing stopping the water from coming in. you might lose the big o ring if you take the unit out. To save the flooding hassle while installing, dive under and plug from outside. So the only thing stopping the boat sinking is a well jammed plug, hmmm

[LeeV]

The amount of water is not that terrible; just takes a little time to remove. As for the o ring, I don't think that will suffice. I didn't measure the difference, but it's substantial, almost as if the transducer needs a "jacket" to slide into to make up the difference!

[sailorchic34]

Don't suppose the blank beside the depth transducer is the sleeve that went for a walkabout from heeling??

[MarkSF]

I put a new DST800 speed / depth / temp sensor in, which of course needed a new through-hull. But if you look in that area now, both the old sensor, and the new one are adjacent to the through-hull!

So the question is : is there another newer speed sensor lying around, that you have not noticed yet? It could have fallen down into the bilge and be out of sight.

[d4raffy]

Pull the other sensor - if they are the same diameter - may give some clues ?


Sent from my iPad using Cruisers Sailing Forum

[HBWT]

On my tacktic set the SOG and temp had a sleeve on it to fit into legacy (B&G) thru hulls. Maybe the sleeve is missing as some have already pointed out. Most all are made by Airmar, you might want to reach out to them with this problem and they will have a better explanation.

[JPA Cate]

Just a detail: the paddle wheel sensor does not necessarily give you speed over the ground, but speed through the water. Your GPS gives you SOG, which, any time you have current with or against you, will be different from what your knot meter reads out, and also affected by set and drift.

If the way the OP's unit worked before was with a temp read out too, that was supplied by a jacket sensor, then possibly the jacket part was either removed for replacement when it failed, or accidentally lost some time ago. HBWT's suggestion, above, could be an effective way of addressing the situation.

Ann

[Captain Bill]

I have a similar issue. I just got a new combination speed/temp/depth transducer with my new Ray Marine instruments. When I went to replace the old depth only transducer I found that the new one was slightly bigger in diameter than my old one. The new one is currently sitting next to my old depth only transducer until the next time I have the boat hauled at which time I will replace the old through hull and install the new transducer. In the meantime I can still get depth only from the old one. Maybe the PO had a similar issue and never got around to changing out the through hull. The new transducer has O-rings that provide a seal and also are spacers. I take it the O-rings are intact on the speed transducer.

[nigel1]

On my paddle wheel, the through hull can either be removed as a complete unit, or, the center part comes out of the "sleeve".
The bottom of the "sleeve" has a non return flap that helps to reduce the amount of water that enters the boat when the center part is removed.
See
http://www.nexusmarine.se/wp-content.../LogTH52mm.pdf

This is similar to the set up I have.

[roverhi]

If the transducer doesn't fit the through hull it's possible the owner replaced the original speed instrument but never got around to installing the through hull for the new instrument's transducer. Any odd through hulls laying around the boat???

As Ann says, the paddle wheel transducer gives you speed through the water not speed over the ground except in no current, no leeway conditions.

[Ziggy]

Originally Posted by LeeV

Installation: I pulled the blank and quickly inserted the transducer. Oh %#@! The transducer has a much smaller diameter than the hole. What the *&^%? Hurriedly replaced blank. Bailed water. Pulled again (idiotic, but I just couldn't believe it!) with same results - definition of insanity.
[...]
Any ideas???!

Are you sure you're not pulling the sleeve with the plug? They are two parts, and both can be pulled out. Normally, the sleeve should stay in the thru-hull when you pull the plug.