Possible to change a T/H transducer in the water?

I think my airmar thru hull transducer is going bad on my Raymarine MFD. Anybody ever swapped one out while the boat is in the water? I'd just be changing the "insert", not the tube.

Dougcole said:

I think my airmar thru hull transducer is going bad on my Raymarine MFD. Anybody ever swapped one out while the boat is in the water? I'd just be changing the "insert", not the tube.

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As long as the bilge is deep enough to hold a few gallons of sea water it shouldn't be a issue.. I used to pull my thru hull to clean the paddle wheel and would swap the blank plug in its place.. clean the paddle wheel then remove and replace the blank with the freshly cleaned wheel. It never was more than a couple gallons to do the entire process.

Hollywood

I'm with Hollywood, no problem. I would unscrew the transducer with one hand and have a towel in the other. As I pull the transducer out I cover the hole with the towel and do the reverse to put the plug in or to return the transducer. I have also spliced a few Airmar transducers in the bilge which is no problem. I located a water tight junction box on a bulkhead.

Yup. Do it to clean the paddle wheel. The newer airmars have a check valve device built in. Barely any leakage at all.

Edit: Wait a minute. Hollywood led me astray. The transducer is separate from the paddlewheel, so no, I haven't. Does airmar make one line that. Might check their website.

As others have said it's not a problem, but 3 things.

1. don't be alone

2. have a plug in reach just in case

3. have positive thoughts like on the Movie "Kellys Heroes"

Always with the negative waves, Moriarty. - YouTube

What function of your transducer do you think is failing? It will make a difference in how you replace it. Mike

I suppose it depends on the style of Airmar Trans. you have. Mine (pictured) is two piece. The inner removable black plastic cartridge is the paddle wheel for the Speedo. and can be taken out from inside the bilge and cleaned or replaced, while in the water with minimal leakage. The outer bronze section is the transducer slug which is installed from outside the hull through a keel block and is bedded in sealer. it also has 50' of cable and a connector on the fathometer end which has to be passed through the keel block from the outside.

I can't imagine trying to pass the 50' of cable and trying to bed the transducer into the keel block while in the water. A better option would be to ask your boat yard to do a lift and hang for you long enough to change out the transducer. If it's someone you do business with, they will probably do it for a minimal fee.

If you have an E or C series I would be looking at the DSM rather than the transducer. They experience a lot of intemittent issues which can usually be solved with modifications to the power supply plug and/or software upgrade.

You will have hell changing that ducer in the water. The fairing block will be 5200d to the brass and everything will be 5200d to the hull. Believe me it aint gonna happen. If you hire a diver he will charge by the hour because he knows its gonna be tuff. You will almost certainly destroy the fairing block. It will more than likely be thru bolted to the hull, its supposed to be anyway, to keep it from turning. Fairing blocks are usually replaced when TH fittings are changed. But, like another posted, its probably not the transducer.

Against a lot of manufacturers recommendations and conventional wisdom, I mounted a transducer on the stern. Since I was experimenting with a Lowrance Structure Scan setup I put the structure scan transducer there also. I saw no problems with this arrangement and the Structure Scan worked very well. About once every two weeks I had to do some cleaning on the paddle wheel to keep the water speed working, but other than that, no problems. I am going to try some transducer paint this summer and see if that makes a difference. I also have a conventional thru hull located to the port of the keel about midships. Either Lowrance MFD can use the structure scan or use the input off either transducer. You just have to be sure what your depth source is. Since the offset from the keel is different from each and I can show that on the screen, that gives me a hint which source is being used without opening some menus.

Except for the distance from the bow to the stern, I don't see any problems with a stern mounted transducer.

Tom

Tpbrady is that a stern mounted thruster? Back to the subject I'm getting ready to install a 740 gps in place of an older Garmin and I'm not sure I'll be able to use the threw hulls I have or if I'll need to pull an put new ones in. Is there anyway to tell what I have by what's in the bildge I know I have some blank pieces of plastic to go in if I pull the transducer out.

David Carter said:

Tpbrady is that a stern mounted thruster? Back to the subject I'm getting ready to install a 740 gps in place of an older Garmin and I'm not sure I'll be able to use the threw hulls I have or if I'll need to pull an put new ones in. Is there anyway to tell what I have by what's in the bildge I know I have some blank pieces of plastic to go in if I pull the transducer out.

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That is a thruster, we have a similar one on our Camano. Also I doubt your transducers compatible.

David Carter said:

I'm getting ready to install a 740 gps in place of an older Garmin and I'm not sure I'll be able to use the threw hulls I have or if I'll need to pull an put new ones in. Is there anyway to tell what I have by what's in the bildge I know I have some blank pieces of plastic to go in if I pull the transducer out.

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N4712 said:

I doubt your transducers compatible.

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Most transducers are made by Airmar and sold with different cable connectors for the Electronics brand. If yours is an Airmar, you can purchase an adapter cable here: Transducer Parts | Blue Heron Marine Electronics

David Carter said:

Back to the subject I'm getting ready to install a 740 gps in place of an older Garmin and I'm not sure I'll be able to use the threw hulls I have or if I'll need to pull an put new ones in.

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What was your old Garmin unit that you replaced? That will give you an idea which transducer you have installed?

Northern Spy said:

Most transducers are made by Airmar and sold with different cable connectors for the Electronics brand. If yours is an Airmar, you can purchase an adapter cable here: Transducer Parts | Blue Heron Marine Electronics

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True, if he has the interchangble type he should be able to just buy another insert I believe?

N4712 said:

True, if he has the interchangble type he should be able to just buy another insert I believe?

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The insert is merely the paddlewheel. The temp sensor and the transducer are cast in resin in the bronze shoe, if it is a B744V, as I am postulating.

The difference is that the existing transducer is likely a 600w whereas a 740 has a 1000w transceiver, so he may not take advantage of the greater depth ability of the 740.

Garmin also sells an 8 pin to 4 pin adapter. Check the ends though, I think my transducer came with the 8 to 4 adapter from Garmin.

David,

It sure is. Hydraulic and works well.

Tom

Northern Spy said:

Most transducers are made by Airmar and sold with different cable connectors for the Electronics brand. If yours is an Airmar, you can purchase an adapter cable here: Transducer Parts | Blue Heron Marine Electronics

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Great link NS

Stashing that one for future reference, thanks.

Most modern transducers are powerful enough to just be mounted inside and shoot through the hull...no special ducer needed.

When I was doing my bottom over..I just yanked the old ducer and filled in the hole....never even planned on putting the new "through hull" ducer through the hull as I really don't need the sensitivity of a fishfinder in a trawler.

Edelweiss said:

What was your old Garmin unit that you replaced? That will give you an idea which transducer you have installed?

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I had a Garmin 2006c. And a separate Garmin dept/fish finder.

I have two of these. I'm not sure where they go. I do have dual stations. My lower is a standard horizon.

Two of the bigger one.

David Carter said:

Two of the bigger one.

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The smaller one is probably a temperature transducer. The larger one has no apparent through hull cross bolting and looks like an older combination fathometer / speed transducer. If it has the correct plug end, it may plug into your new unit and work ok. Garmin 2006 chartplotter was designed to be used with a sonar unit. Somewhere on your boat there is most likely a sonar module, probably a Garmin GSD20. The transducer may be plugged into that. I'm not familiar with a Garmin 740 and don't know if it will run off the GSD20. That would be a question for Garmin Customer Service, but I would think you would want to connect the transducer directly to your new unit.

But as someone else has pointed out, it won't give you the performance of a new dual frequency transducer. Your Garmin 740 is capable of up to 1 KW operation and will provide you much greater sensitivity and definition. I would replace it at your earliest opportunity.

psneeld said:

Most modern transducers are powerful enough to just be mounted inside and shoot through the hull...no special ducer needed.

When I was doing my bottom over..I just yanked the old ducer and filled in the hole....never even planned on putting the new "through hull" ducer through the hull as I really don't need the sensitivity of a fishfinder in a trawler.

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My plan exactly and the existing transducer is on the stern of my boat That is about the only really quirky choice I've found on my boat. Not sure what brainiac convinced the previous owner to mount a ducer on the stern? Especially in my skinny water.

psneeld said:

Most modern transducers are powerful enough to just be mounted inside and shoot through the hull...no special ducer needed.

....never even planned on putting the new "through hull" ducer through the hull as I really don't need the sensitivity of a fishfinder in a trawler.

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One of those "Aha!" moments for me, reading that. Right. All I need is to see the depth of the water, and could not care less about the contours of the bottom nor of all the critters down there. May they swim in peace -- I will eat their kin in restaurants with great enjoyment, but they can swim underneath my boat in perfect safety.

The big one looks like an Airmar transducer, with a water speed paddle wheel. There should be a number on a tag on the cable somewhere, usually close to the td. It could be a 600 or possibly a 1000 watt, or a tilted element unit. Unless it is on a fairly flat (horizontal) surface I would guess it is a tilted element unit, lack of an inside fairing block anyway.

kulas44 said:

The big one looks like an Airmar transducer, with a water speed paddle wheel. There should be a number on a tag on the cable somewhere, usually close to the td. It could be a 600 or possibly a 1000 watt, or a tilted element unit. Unless it is on a fairly flat (horizontal) surface I would guess it is a tilted element unit, lack of an inside fairing block anyway.

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It is on an angle and it has a twin on the other side of the bildge. What is a tilted element. I have plastic pieces about 6" long that look like they go into this unit as a blank. It would be nice if I could somehow ping the wires to find out which one goes to which sonar or gps.

Edelweiss said:

The smaller one is probably a temperature transducer. The larger one has no apparent through hull cross bolting and looks like an older combination fathometer / speed transducer. If it has the correct plug end, it may plug into your new unit and work ok. Garmin 2006 chartplotter was designed to be used with a sonar unit. Somewhere on your boat there is most likely a sonar module, probably a Garmin GSD20. The transducer may be plugged into that. I'm not familiar with a Garmin 740 and don't know if it will run off the GSD20. That would be a question for Garmin Customer Service, but I would think you would want to connect the transducer directly to your new unit. But as someone else has pointed out, it won't give you the performance of a new dual frequency transducer. Your Garmin 740 is capable of up to 1 KW operation and will provide you much greater sensitivity and definition. I would replace it at your earliest opportunity.

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The sonar is a Garmin 240

David Carter said:

The sonar is a Garmin 240

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fish finder 240

Ok. . . If you don't have a GSD 20 or later (pictured) then it doesn't sound like the previous owner installed and connected the transducer to the Garmin 2006 and he had a separate fathometer Garmin 240 connected to one of the large transducers and your flybridge fathometer attached to the other. Is that a correct assumption? This is all obsolete (non supported) equipment now, so you need to decide what you want to do with all the old gear. Remove it or if it still works, keep it in place as a back up??? What were you planning?

If you can connect the old transducer to the Garmin 740 it may be all you need for now. But you have some choices to make. If you're not sure, maybe you should have somebody knowledgeable come aboard, inventory your electronics and give you some ideas.

The plastic blanks you have are used to replace the paddle wheel speed sensor. You unscrew the large plastic cap nut on top of the transducer and using the metal ring pull out the plastic paddle wheel speed sensor shaft. The plastic blank is placed back into the transducer tube and the cap nut screwed back down to keep water from entering the bilge. Sometimes the paddle wheel gets fouled or broken and it needs to be serviced. In the Garmin owners manual they actually recommend that you remove the paddle wheel sensor when the boat is not in use. I've removed mine once since installing it.