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Old transducer question

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pboily
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Initially Posted - 06/20/2024 : 02:49:46

My Catalina 25 (1984) has an old through-the-hull transducer, with a 7-pin connection (it may date from the 1980s). Does anyone know if it is compatible with a modern instrument? I would rather leave it in and use it than installing a new transducer.

Voyager
Master Marine Consultant

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Response Posted - 06/20/2024 : 06:13:20

Do you still have the original depth meter display and electronics? If so, what brand and model is/was it? That may help ID the transducer a little easier.
What level of electronics do you feel comfortable with? Wiring components, using a voltmeter, using an oscilloscope, designing new circuits?
Frankly, what many of us did was to was to leave the old transducer in place, and replace the display and transducer with another unit. Because ultrasonic pings travel both through fiberglass and other materials, you can mount the transducer inside the hull, shoot vertically through it, and get a good depth signal back to the display.
The one thing that the transducer DOESN�T like is an air gap. So many folks have used the wax ring used to secure toilet bowls on the drain (available at hardware and home centers) to bed the transducer on the bilge floor to remove the air gap.
However, if you can find out how to use the original transducer with a new display unit, let us know too! Hmmm seven wires, what could they do: Power, ground, pulse generator (2 wires?), pulse pickup (2 wires), another signal or control wire? Hmmmm

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

pboily
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Response Posted - 06/20/2024 : 07:05:47

Thank you very much for the reply.
The original display etc. are long gone (2-3 owners back). The reason that I am exploring the option of using this transducer is that I cannot find a location that gives us a signal for a glue-on depth transducer (Hawkeye). The transducer works when put in the water overboard. We can hear the "clicks", and we verified that the unit is getting the appropriate voltage (a little over 12v).
We tried the water bag, vaseline and toilet seal wax methods to test various locations. We tried under the v-berth, multiple locations under the stairs near the winch cable, port cabin locker. No signal anywhere. This is very frustrating.

Photo of old cable connector is here:
https://www.facebook.com/photo/?fbid=122158264448058447&set=gm.1847930695682918&idorvanity=225943071215030&__cft__[0]=AZVj9NKJp9GP1AjyRn--9GNjP3b4W1uvAn7u61HR8GmN-xbjc8taTOzlQ4kG3FDtcW8iNIbqxlH3hKGSaU3HdqE0F2b-tBhwHdJanijsWETXDMVDGyiq6mTzTzMctR0--LuN-6dTjzqZmfsV4uofzUv-lduztfEYqkIXJ30i_zmyn7z9sqXMmM1oPIcCcW0zVDUwNHGQQcB5Yrca7pILEVPH&__tn__=EH-R

Edited by - pboily on 06/20/2024 07:06:40

islander
Master Marine Consultant

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Response Posted - 06/20/2024 : 16:51:50

This U Tube video knocks the in-hull (glue inside the hull with toilet or the other methods you tried. Sailboats have very thick hulls so can be why you got mediocre results.
https://youtu.be/sSAAUfe05WE?si=SCY9PE8_TVFWC4mT

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 06/20/2024 16:54:21

OLarryR
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Response Posted - 06/20/2024 : 21:50:07

I listened to the video that is negative on use of in-hull transducers and I do not fully agree with the assessment. What I do agree with is that if you cannot get a good signal utilizing an in-hull transducer after many unsuccessful attempts, then you may have to go with a thru hull or transom mounted transducer.

I bought and installed my Humminbird Fishfinder with an in hull transducer back in 2005-2006 timeframe and it has worked flawlessly ever since then and I have never had to renew or rebed the transducer in the wax ring material I used between it and the hull (under the VBerth area adjacent to where my original depth finder thru hull transducer is located (no longer used).

The instructions that were provided with my Humminbird fishfinder provided what I believe is a better understanding of how my in hull transducer functions compared to same mfr's thru hull transducer. It did not state that the in hull transducer provides inaccurate readings or cast doubt regarding its performance. What it indicated is that the signal strength is reduced and the in-hull transducer provided with my fishfinder would be accurate up to a depth of 400 ft, whereas, the thru hull transducer would be accurate and able to read down to a depth of 1000 ft.

When I installed my fishfinder, there is a procedure to set/readjust its readings but I decided to leave it as is since it reads about 1 - 1 1/2 feet less than actual depth but where the transducer is installed, the hull (at the VBerth area) is probably at least 1/2-1 foot below the waterline. I compared depth readings dockside with lowering a telescopic pole and taking measurements. Also compared chart depths for my waters with fishfinder readings. So, my fishfinder readings may read a bit less than actual depth, but I prefer a slightly, if at all, conservative reading.

Not sure why you are having trouble utilizing an in hull transducer. Some have had issues installing and using an in hull transducer but usually they eventually find a suitable hull location. Could be many factors and I am no expert as to what could be the cause: Maybe your hull is a vintage that had a thicker hull thickness or hull fiberglass laid up somewhat differently or maybe different fishfinder brands and transducers have varying signal strengths with some in hulls transducers more prone to signal errors versus hull thickness.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 06/20/2024 22:06:13

islander
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Response Posted - 06/21/2024 : 07:33:56

They do sell adapter cables. Do a search for transducer cable adapter, 7 pin to what ever you need on the head unit. I wouldn't assume that the thru-hull transducer is bad. Is there a label or printing on the cable that might give you a clue to the make or model?

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 06/21/2024 07:42:38

Voyager
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Response Posted - 06/21/2024 : 08:18:12

Mounting the transducer to the outside of the transom should be your best bet. Now, routing a cable from your cockpit bulkhead or other display panel area on the boat back to the transom without having a cable exposed becomes the challenge.

On my boat, Passage, there are two routes I�d consider: the manual bilge pump hose runs between the port-side fender locker (aka the dumpster) and the quarterberth. There�s a thin piece of plywood separating them. This hose attaches to a through-hull fitting on the transom above the waterline. If you can put a tee somewhere along the downstream portion of the hose past the outlet of the pump, you can probably fish the cable through it and back up to the display.

Once you have the cable in place, fill the tee opening with caulk or putty to allow the bilge pump to work when you need it without leaking. Don�t overfill it, as it can block the bilge pump action.

The other route would be simpler. Run the cable through the grommet where your outboard charging cable runs. I have an electric start and 12A alternator in the outboard, so someone before me drilled a hole through the transom above the engine mount, and put a rubber grommet on the hole to keep out the elements.

Your boat may not have this option, but you could do it yourself. To position the hole at the highest point on your transom, get yourself down in the quarterberth with your drill using a very thin drill bit, and put the drill up as high as you can reach. There�s a piece of the cockpit seat that comes down there, so you really have to finagle the drill. Drill VERY slowly with minimal pressure to avoid cracking the gelcoat on the outside. Afterwards, from the outside, gradually enlarge the hole using larger and larger size drills. Tape the outside of the transom to prevent marring of the gelcoat.

Then run your cable.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

islander
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Response Posted - 06/21/2024 : 10:47:18

quote:
Mounting the transducer to the outside of the transom should be your best bet

How are you going to do this. Our transoms are fully above the waterline so where would you mount it. Mounting it deep enough so its in the water and clear of any turbulance and air bubbles and how about healing or going over wakes and chop pulling it out of the water. This photo shows where the waterline is. Its the little white stripe above the black bottom paint. Above that is the blue boot stripe.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 06/21/2024 10:49:38

OLarryR
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Response Posted - 06/21/2024 : 20:43:31

It certainly does look like the transom area for mounting would be above the waterline or at least an area of turbulence that may interfere with readings. I would definitely want to know who on the forum has utilized a transom mount and what their experiences with the install and utilization has been. There should be some that have gone this route.

Going back to the original question about utilizing the 7 pin connector. Many Cat 25s were outfitted with an SR Mariner instruments. But this was an analog depth finder and believe it did not have a pin connector but just a cable with 2 wire leads to be hooked up to the display. I did a brief search on the web and came up with some references to newer depth finders utilizing old transducers with an 8 or 9 pin connector. The posting indicated that some of the pins could be dummy pins (not used) and so an adapter connector was utilized that had I believe 8 pins on one side but 6 pins on the other that hooked up to the newer depth finder. But the signal frequency has to match and so the original depth finder mfrs model needs to be identified. In any case, I then found at least one older depth finder mfr that indeed utilized a 7 pin connector - Lowrance. But not sure how many others utilized a 7 pin connector...and you would still need to determine the signal frequency before any possibility of utilizing the old transducer. The info may not be useful but wanted to let you know what I was able to find & not find.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 06/21/2024 20:46:11

GaryB
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Response Posted - 06/21/2024 : 22:28:54

quote:
Originally posted by pboily

Thank you very much for the reply.
The original display etc. are long gone (2-3 owners back). The reason that I am exploring the option of using this transducer is that I cannot find a location that gives us a signal for a glue-on depth transducer (Hawkeye). The transducer works when put in the water overboard. We can hear the "clicks", and we verified that the unit is getting the appropriate voltage (a little over 12v).
We tried the water bag, vaseline and toilet seal wax methods to test various locations. We tried under the v-berth, multiple locations under the stairs near the winch cable, port cabin locker. No signal anywhere. This is very frustrating.

Photo of old cable connector is here:
https://www.facebook.com/photo/?fbid=122158264448058447&set=gm.1847930695682918&idorvanity=225943071215030&__cft__[0]=AZVj9NKJp9GP1AjyRn--9GNjP3b4W1uvAn7u61HR8GmN-xbjc8taTOzlQ4kG3FDtcW8iNIbqxlH3hKGSaU3HdqE0F2b-tBhwHdJanijsWETXDMVDGyiq6mTzTzMctR0--LuN-6dTjzqZmfsV4uofzUv-lduztfEYqkIXJ30i_zmyn7z9sqXMmM1oPIcCcW0zVDUwNHGQQcB5Yrca7pILEVPH&__tn__=EH-R

Using the toilet bowl wax method you have to be careful when pressing the transducer into the wax. It's very easy to get some air/air bubbles between portions of the transducer face and the wax. Doing so will prevent you from getting a reading.

When using this method cut a section of the wax and handle it as little as possible. Place it very slightly to one side of the centerline of the hull under the v-berth so it's not straddling the V.

Press the transducer straight down into the wax at least 3/4 of the way thru the wax twisting it back and forth very slightly as you do so. Make sure you don't push it all the way thru the wax.

I believe I remember using this procedure and it helped minimize the risk of getting any air bubbles. If I misspoke hopefully someone will correct me.

Hopefully you'll be able to use your old transducer and not have to retry the wax method! Good luck and let us know if you find an answer.

Association Member

GaryB
Andiamo
'89 SR/WK #5862
Kemah,TX

Edited by - GaryB on 06/21/2024 22:31:23

pboily
Deckhand

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Response Posted - 06/22/2024 : 02:52:09

Thank you everyone for all the feedback.

Update:
I found the label on the transducer cable.
Images here:
https://photos.app.goo.gl/52V3Spt7MHrzh2EJ8
https://photos.app.goo.gl/fVxshpyfMp4FgUiW7

I'm quite sure that is an "Airmar/Apelco Raytheon B44 200 Khz 10015 Triducer 7 Pin - Bronze Thru-Hull Transducer" (I found many on ebay and on the web). However... I now think that what I have is the blank plug, not the actual transducer, because mine did not have a speed paddle (boat is in the water now and can't take a photo of the underside, but I'm sure it was flat on the bottom). I just don't understand how the cable would connect to the transducer given that the cable goes through the brass fitting.
Image of the transducer, view from the bilge:
https://photos.app.goo.gl/AJG7HWwvLxVWd6WA9

In any case, I will retry the toilet wax method more carefully. That seems to be my best option at this point.

Thank you again everyone for the feedback.

Edited by - pboily on 06/22/2024 03:22:30

islander
Master Marine Consultant

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Response Posted - 06/22/2024 : 04:51:52

According to what I came across is that Airmar made/makes the majority of the transducers.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

OLarryR
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Response Posted - 06/22/2024 : 06:33:04

I am now a bit confused if we are talking about a knot meter or a depth finder transducer. You mentioned paddle wheel - then we are talking about a knot meter transducer. But in the postings, thought we were talking about a depth finder transducer. Oftentimes, both instruments are made by the same mfr as my original instruments were SR Mariner. SR Mariner got out of the marine business many years ago but still exists on Long Island making instruments for the health industry. Up to a few years ago, they actually were still supporting the SR Mariner line with whatever parts they had available. Not sure when but probably about 15 years ago or so, I talked with them about my non-functioning knot meter and I was able to send it to them and they reconditioned it - Like new! So, my knot meter is still SR Mariner and has continued to function. Then about ~ 5+ years or so ago, during pressure washing, wrecked the paddle wheel. I was able to get a replacement paddle wheel/transducer from SR Mariner but.......I have procrastinated installing it.

Between the two instruments, the depth finder is obviously the more important of the two for safety reasons/running aground, etc. As far as the knot meter - You can always get by with portable GPS unit or whatever or do without. But the depth finder or fishfinder is a necessity.

Agree with Gary - Keep trying to utilize an in hull transducer for depth readings. I would have reiterated that again, above, but did not want to get too pushy with my own thinking. It did cross my mind that some depthfinders/fishfinders these days have become very sophisticated in what they actually can read. My Humminbird fishfinder was a fairly unsophisticated unit. just took depths plotted on the screen, no forward addl ,measurements, etc. Not sure about it's strength signal versus newer units and if newer units are more finicky but I just pushed the transducer into wax ring material.smooshed it around and it has worked ever since. If your bottom paint is peeling or you have blisters or whatever that interferes with a solid transmission thru the hull/gel coat/paint, then that may interfere with readings. I never had issues...except one time which is of interest - The one time my boat was out for the winter season, I had it out for major hull blister repairs - You can see photos of the repair - A real horror story! Anyway, when work was completed, 7 coats of Interlux Interprotect applied and then anti-fouling paint, the boat was again back in the water. I prepped my boat for departing the next day to go back to my marina and I noticed when I turned on the fishfinder, it was not reading. Hmmm.......well they had just lowered the boat into the water earlier that day and I noticed a whole bunch of micro-bubbles alongside the hull. My hope was that maybe same existed under the hull and perhaps that was interfering with the fishfinder readings. The next morning I took off from the Marina that performed the repairs. I noticed the micro-bubbles were gone and my fishfinder was reading fine again...and has ever since.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 06/22/2024 06:46:03

Voyager
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Response Posted - 06/23/2024 : 07:03:09

Most transom mounts provide a bracket with an offset arm to put the transponder under the water. My fish finder used this arrangement.
FWIW, It took me several tries using the toilet bowl wax method. If you work the wax too much, you�ll knead in air bubbles into the wax, and this will fail. If that happens, get a fresh piece of wax that completely covers the face of the transponder and mash it down real good. Of course, the clearer the mounting surface, the better, so proper prep is important.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 06/23/2024 07:12:28

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