Transducer replacement

Going on the hard for a short refit(~2 weeks) mainly for bottom painting. Will also be replacing depth sounding transducer (old one has been a bit erratic of late).

'99 Maxium 4100 SCA, used for pleasure cruising up & down AICW/The Keys. I'm not a fisherman, so no need for accurate 'fish finder' or any type of structure/3D or forward looking. All other helm electronics (auto pilot, electric compass, radar, etc) are SIMRAD, so I'm looking to stay SIMRAD.

The xducer I'll be replacing is mounted on a (please see images to correct me, if necessary) thru-hull fairing with the bottom of the fairing parallel to the 'bottom'.

All that being said, I am at a complete loss for how to proceed now - YouTube videos haven't been much help - in selecting a replacement (I believe a frequency selectable broadband CHIRP xducer would suit me best). I guess my main 'need' for knowledge is how to determine the correct xducer to 'fix' my fairing and how to take out the old one and put in the new one.

It would certainly have been helpful for me to have measured the current transducer last time I had the boat out of the water, but I didn't do that. One thing of interest for the old xducer is that it had a speed wheel (log) in the center that might help someone identify what I currently have to help with selecting a replacement. Also, again, please correct me if I'm wrong - from the external pictures, I believe I see a fairing that's flush with the hull, and then the actual xducer mounted to it.

Internal

External

It will depend on which transducer will work with your sounder or MFD. they make ducers now wilt a tilted array so you can mount them flush without a fairing block. The tilted array looks straight down instead of sideways. You do need to know the deadrise of the boat so you can match the tilt angle to the angle of the hull. Much easier than using a fairing block. Don’t know if they will work with chirp or not though.

There should be a label on the transducer wire that identifies the type of transducer. The label is usually 3’ from the end of the cable. Start at the transducer and follow the wire for 6’ and see if you can find the label. If not go to the instrument end and try there. It looks like an Airmar Transducer.

I just did this and it’s pretty straightforward. I had the yard do it and they had it done a couple of hours, which means I would only have taken 2 days.

1) the new transducer can have the same footprint and in my case, even use the same faring block, even though I moved from a Raymarine to a Furuno fish finder. I seriously think you should consider using a simpler technology, similar to the one you have when choosing a transducer. I think the Chirp stuff is way over priced unless you need those features. A simple 2 frequency transducer should be sufficient.

2) It should be held in with Sikaflex 291 and the bottom paint should be cleaned off beneath the faring block. If the old one is held on with 291, as it was in my case, you cut the chord of the old transducer and simply hammer out the old one. I’m

3) the faring block will come in two pieces, inside the boat and outside the boat. In my case I reused the same faring block. It was a match for the replacement transducer. The transducer will slide inside a plastic sleeve that is part of the inside part of the faring block. The outside faring block and the transducer are mounted over Sikaflex 291 to make a watertight seal. The transducer and faring block are held in place.with the hexagonal threaded ring that is visible in the inside photo. I think it is a mistake to use 3m4200 or 5200 in this situation.

Talk to the yard. You might find it’s worth using them for this procedure. The charged for 2.5 hours labour. A bargain in my opinion.

Jim

The transducer in the picture appears to be a fixed thruhull with a removable transducer "core". Unscrew the plastic collar and the transducer core should pull out, though it's probably a bit stuck and will require some effort.


As previously mentioned, there should be a tag on the cable near the transducer end with the part number. With that, you should be able to figure out s replacement that will fit in the existing thruhull and fairing with no changes to either.

Virtually all transducers are made by Airmar and are distributed by Gemeco. It is worth your time to explore the Gemeco website. This was copied from the Gemeco website:

Transducer ID Labels
Every Airmar transducer has a label attached to its cable, located near the top of the transducer or where the cable plugs into the back of the instrument or display. This label contains information that is helpful in identifying the transducer and locating the correct service parts for it. For most Airmar products this label will show
the model name
the manufacturing date
certain performance characteristics (i.e. the transducer's frequency)
the Airmar part number (PN)
a Customer Part #
Airmar sells many of its transducers through electronics manufacturers that often create their own part numbers. The 'Customer Part #' shows that reseller’s part number information.

The back of the tag will typically show the product's unique serial number along with a bar code. This serial number can be useful for determining detailed information that is not present in the part number, such as exact date of manufacturer and the original purchaser of the transducer. There have been multiple label formats used through the years but all of these formats have contained the Airmar Manufacturing part number that uniquely identifies the exact configuration of the specific transducer in your possession.

In all cases it is the Airmar Part Number (PN) that is the most important number to have available when ordering parts or contacting us about the transducer.

Thank all ... I haven't seen any tag near the thru-hull, I'll check where the xducer cable connects to the NMEA bus. I'm kicking myself for not doing a better look last time the boat was out of the water, but at the time I really wasn't thinking about replacing the xducer. Live in learn. Just hoping the purchase/shipping doesn't take too long (if I can't determine current xducer) and keep us on the hard ($$$) for longer than necessary.

PJHoffnet said:

Thank all ... I haven't seen any tag near the thru-hull, I'll check where the xducer cable connects to the NMEA bus. I'm kicking myself for not doing a better look last time the boat was out of the water, but at the time I really wasn't thinking about replacing the xducer. Live in learn. Just hoping the purchase/shipping doesn't take too long (if I can't determine current xducer) and keep us on the hard ($$$) for longer than necessary.

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Unless your hull is other than a solid Fibreglass layup, putting the transducer in a pipe, cut to the proper angle, epoxied to the inside of the hull will give you excellent results. That will save messing with the angled blocks, protrusions from the hull, haulouts, etc.

Hey, the tag was there ... but pretty much unreadable. BUT - with a strong flash light and a magnifying glass I was able to ID the xducer as an old Airmar B44V. That model is discontinued, but the newer B744V is my 'almost' right replacement. The external fairing is slightly different size, so I'll have to do a swap. Thanks to all for the help, will let you know how things go once we're on the hard.

PJHoffnet said:

Hey, the tag was there ... but pretty much unreadable. BUT - with a strong flash light and a magnifying glass I was able to ID the xducer as an old Airmar B44V. That model is discontinued, but the newer B744V is my 'almost' right replacement. The external fairing is slightly different size, so I'll have to do a swap. Thanks to all for the help, will let you know how things go once we're on the hard.

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Good. It’s the ID of the hole that’s the issue. If they are the same, it’s pretty straightforward. The replacement transducer may even come with its own faring block. Just makes sure that you remove the bottom paint where the faring block sits.

Jim

Ready to replace

JDCAVE said:

Good. It’s the ID of the hole that’s the issue. If they are the same, it’s pretty straightforward. The replacement transducer may even come with its own faring block. Just makes sure that you remove the bottom paint where the faring block sits.

Jim

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Spoke with an Airmar tech and holes are the same, different fairing block shape. On the hard on Thursday, hope to have the xducer and fairing out (planning nice gentle 'tapping' with a set of paint scrapers around the perimeter until it pops off) by Friday to make way for the bottom P&P.

Thanks again to all for your help. Will let ya know how it goes.

PJHoffnet said:

Spoke with an Airmar tech and holes are the same, different fairing block shape. On the hard on Thursday, hope to have the xducer and fairing out (planning nice gentle 'tapping' with a set of paint scrapers around the perimeter until it pops off) by Friday to make way for the bottom P&P.

Thanks again to all for your help. Will let ya know how it goes.

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I mentioned it earlier, but your existing transducer appears to be a two part transducer with the thruhull separate from the transducer itself. These are handy because you do not need to replace the thruhull or fairing block to replace the transducer. You just remove the locking ring on the transducer, and pull it out of the thruhull. Then insert the replacement and you are done. It literally takes seconds, and is typically done with the boat in the water because you can swap them quickly.


Now yours is old enough that the thruhull may not be compatible with current cores, in which case you will need to replace the thruhull and fairing block. But I really encourage you to research this because replacing it may be much, much easier than what you are currently planning.

No problem. Yours is a removable type. There is normally a blank mounted close by.

Just slacken the hold down about 1/4" pull up and turn slightly to break the barnacles before pulling straight up. Normally there is a niche to sit it in for speedo fore and aft alignment, if yours has a ultrasonic speedo. Take it out and drop the blank plug in. If its heavy in growth maybe that's your problem?

So, it wasn't easy to get out - had to cut the retaining nut.


But finally got it out


New one, 744VL, installed easily.

Glad you got it in. I just cut out 2 old transducers and glassed the openings closed. I used a multi tool and a grinder with a cutoff blade and had to cut off the transducers and the wooden blocks they used to fair the transducers in.

Wasn't sure if this was more appropriate in this forum or the EE&N, so I'll start here.

Finishing up on the hard, replaced xducer and finished bottom painting. I taped off the 'face' of the xducer (rubber part) to prevent any bottom paint getting on it. Will now finish off covering the fairing block with Pettit 1793 transducer paint.

One thing I'm unsure of is whether or not the rubber face of the transducer gets painted (area circled in the image). It would seem to me the answer is no, since it would interfere with the outgoing ping and echo return. If not, then how do I protect this area from growth?
https://i.imgur.com/EpOhri4.jpg

To close out this thread - with a big smile.

Used Prop Speed Foul Free paint on the hydrophone face.

The biggest reason I wanted to replace my sounder was it's inability to get returns when I was on plane. Well, splashed the boat on Tuesday and ran back to the home marina on Wednesday and I certainly had a smile on my face with the fathometer holding the bottom just fine (10-12ft) for about a half an hour on a 20kt run. No issues at all on my return to home slip (depths 5ft to 25ft).

Thanks to all who supplied input along the way.

You know, unfortunately the bloody things just wear out over time. They aren’t just electronic. They produce sound energy at high frequencies and the ceramic elements wear out over time. Maybe they just rattle themselves to death.

I managed a hydroacoustics program in my past life. These units ran 24/7 for 3 months a year. I can’t remember whether they were on a 5, 8 or 10 year replacement scheme but replacement was in the budgets.

Jim