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Author Topic:   SONAR Transducer: Through-hull installation on 16-foot Unibond Hull
Mr T posted 06-01-2012 03:49 PM ET (US)   Profile for Mr T   Send Email to Mr T  
I’m rather leary of the idea [of installing a through-hull SONAR transducer on a 16-foot Boston Whaler Unibond hull] and wanted to solicit input from all of you. If I do go this route I was thinking of installation in the tunnel back by the motor well. Any thoughts?

When I do a search on the site here using the terms "through hull transducer Nauset Montauk," I cannot find any evidence of anyone doing it--most threads caution against it.

[Some background information on why there is interest in a through-hull SONAR transducer on a 16-foot Boston Whaler Unibond hull.]

I am running a Raymarine A65 multi-functio SONAR and chartplotter unit on my 1969 Nauset hull. Currently it is using the factory supplied OEM Airmar model P58 transom-mount transducer. I am now faced with the [situation] of having to replace that transducer a third time. The symptoms I am experiencing are a loss of bottom tracking when running the unit in the 50-KHz display mode while fishing lakes with downriggers. What is happening is that the unit will lock on to the returns from the downrigger balls, and not the actual lake bottom. I have been discussing with my local electronics expert and he tells me that the OEM P58 is not built to the same level of quality as the aftermarket P66 unit, and the element is delaminating from the housing, thus causing this [problem of tracking the echo from the lead balls instead of the lake bottom]. When I had this situation occur three years ago, I replaced the P58 with another one of the same model, and the symptom went away. The problem I am facing is that the P66 aftermarket unit is no longer available with the correct plug for a Raymarine A-series unit. The only options available are:

--another P58 transom mount transducer

--the P79 through hull unit, made of plastic

--the B60 through hull unit, made of bronze.

The P79 and B60 options are the same quality build as the P66, but they would require drilling into the hull to install them.

dfmcintyre posted 06-01-2012 05:21 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
I've seen the following method used once [to install a through-hull SONAR transducer in the Unibond hull of a Boston Whaler]:

Slightly off centerline, adjacent the rigging tunnel a 4" hole saw drilled through the glass and wood. The remainder of foam was removed by hand, down to the bottom of the outer hull. Additional glass was hand layed in, so the hull layer was approx 1/2" thick. of plastic pipe, 4" od was inserted and a secondary hole was drilled between the rigging tunnel and the new 4" pipe. Cap of some sort of plastic was fabricated. The transducer was mounted (I cannot recall if it was shimmed level with wood underneath or not), cable routed and cap was screwed down.

Oh, and the pipe was well caulked, minimizing any chance of water penetration around the bottom and top.

Owner liked the installation, and said it worked well for him.

Another technique I've read about, is to build a cavity (maybe in this instance, use a larger diameter pipe...), fill it with a lightweight oil and mount the transducer in the oil bath. Supposedly there is a slight degradation of the signal, but if it's a fairly thin skin, the signal will still go out and return.

I suppose you could try the oil technique, before doing the drill through. I would also keep it well away from any portion of the hull where a trailer bunk might come in contact with it.

Only caution I'd have is if the hull is in excellent condition, would you want to lower it's value.

If you end up trying those techniques, let the forum know!

Regards - Don

Tom W Clark posted 06-01-2012 05:48 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Be careful: 243275d1338214367-cant-good-whaler-transducer-lift-point-photo-3-.jpg

kwik_wurk posted 06-01-2012 06:35 PM ET (US)     Profile for kwik_wurk  Send Email to kwik_wurk     
I would be worried of a blow-out on the through hull.

I have heard of it happening on sailboats with transducers mounted in front of the keel.

On a Montauk I would be worried about launching off a wave and landing hard creating enough water pressure to blow it out.

But if you build it up enough hopefully it won't happen.

dfmcintyre posted 06-01-2012 07:26 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Tom -

Thanks for the photo. Shows exactly why I mentioned that he might want to make sure he's well away from the trailer skid area(s).

On our 25 Revenge, there was a spot the factory glassed in a block of wood for a through hull install. To access it, you first removed the small deck / floor area in the cabin. From what I recall, it was a depression towards the rear of the area. There was also a drain through hull in the same area. Had to build up an angled block out of mahogany so it wouldn't shoot sideways!

Regards - Don

Commander Coo1 posted 06-01-2012 07:45 PM ET (US)     Profile for Commander Coo1  Send Email to Commander Coo1     
what would happen if you fabricated a transom mount for the thru hull transducer? possibly a box witha fiberglass bottom?
contender posted 06-01-2012 09:08 PM ET (US)     Profile for contender  Send Email to contender     
My only question about drilling through the hull would be if the threads on the sender would be long enough to be able to attach the nut. (whaler hulls are thick) Airmar makes all kinds of senders you need to figure out the angle of the place were you wish to install the sender. I think the sender are 0-5 degrees, 5-25 degrees and 25 degrees or greater. The through hull bronze is the best way to go, I would use 3m 5200 to seal the unit and let it sit up for 2 week to cure properly. I kinda like commander's idea but this may give you the same problem because of the location.
jimh posted 06-02-2012 06:22 AM ET (US)     Profile for jimh  Send Email to jimh     
There are two concerns with installing a through-hull SONAR transducer on a 16-foot Boston Whaler Unibond hull:

--most 16-footers are trailer boats

--the thickness of the Unibond hull double bottom

Any SONAR transducer installed as a through-hull on a boat that will be stored, launched, and retrieved from a trailer must be carefully placed so as not to be in a position to interfere with the trailer supports or to be damaged in the normal course of launching or loading the boat. This will constrain the mounting location.

The double bottom hull construction of the Unibond hull of a Boston Whaler boat creates a substantially thicker hull section for a through-hull transducer to span. I cannot offer a non-destructive testing method for determining the thickness of the double bottom at a particular location. I think you could be surprised by the thickness of the double-bottom. I may be prudent to make a very small test hole drilling at the intended installation location to make an accurate measurement of the thickness of the double bottom hull at that point. If the hull proves to be too thick, it would be a lot easier to repair a 1/8-inch test hole than a 2-inch-diameter bore.

jimh posted 06-02-2012 06:37 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding the quality of SONAR transducers sold under the AIRMAR brand name as compared to identical transducers sold under private label brands and made by AIRMAR, I cannot offer any authoritative comment. I am skeptical that private label transducers made by AIRMAR would be of lower quality than the ones AIRMAR sells under their own brand name. Devices that are given different model numbers and are sold with different specifications could certainly be different.

As a general rule one does not find a lot of 16-foot boats using through-hull SONAR transducers. The transom mount SONAR transducer has been shown to be an entirely satisfactory and very practical solution for smaller boat that are stored on trailers. I would be guided the preponderance of experience of others--stay with a transom mount SONAR transducer.

Mr T posted 06-02-2012 10:12 AM ET (US)     Profile for Mr T  Send Email to Mr T     
It appears that the consensus is to stay away from a through hull which I agree with.

Both models are sold under the Airmar label.

Tech data from Airmar uses the same electrical reference sheet.

The P58 is listed as a low price alternative.

The P66 is listed as the best performing, most popular transom mount.

Performance data on the spec sheets are, to my eye the same.

jimh posted 06-02-2012 11:56 AM ET (US)     Profile for jimh  Send Email to jimh     
If AIRMAR sells two products with different model designators and at different prices, it is fair and reasonable to assume that the more expensive one should offer some advantage. I am not sure if you are suggesting that something contradicts that assumption in these two models and their prices.
Mr T posted 06-02-2012 03:44 PM ET (US)     Profile for Mr T  Send Email to Mr T     
The person I am working with is a long time vendor of all major electronics. According to him the difference is in the amount and application of the epoxy used for bedding the element itself, which lends itself to longer life as a result. That is the fair and reasonable advantage to the higher cost item. Essentially the OEM P58 model is made at a lower manufaturing cost to allow for better pricing when bundled with certain electronic units. My A65, while not cheap, is an entry level unit compared to the C and E series units that were available at that time. I am frustrated that I cannot purchase the P66 only because the mfr. decided to use a specific connector to preclude customers from being able to update to the better built P66. I am not suggesting the "performance" of the P66 is better, just that the build quality is higher.

jimh posted 06-02-2012 06:30 PM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the further explanation re the connectors. I guess I did not read your initial article with enough care to catch that the first time.

I am not an expert on AIRMAR, but I was under the impression they have a line of transducers with a universal connector, and they also sell adaptors that convert the universal connector to specific brand device connectors. I think you ought to check with AIRMAR to clarify the options available to you, if you haven't already.

K Albus posted 06-02-2012 07:41 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Have you tried contacting Airmar directly? I have contacted them in the past and they were very helpful.

In a separate incident, I also contacted Rule directly at one time regarding a discontinued livewell pump that I had been unable to find for sale anywhere. Rule happened to have a few of the discontinued pumps laying around, and they sent me one for free. Maybe Airmar has some leftovers of the P66 with the connector you're looking for.

Mr T posted 06-03-2012 12:58 PM ET (US)     Profile for Mr T  Send Email to Mr T     
I sent an email to Airmar last week about the issue I am facing and await a response, which I will relate back to the board. I am convinced that regardless of the answer, I am not going to pursue installation of a through hull transducer.
bluewaterpirate posted 06-04-2012 09:41 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
The reason the P66 is no longer compatible with your Raymarine unit is Airmar added ID TM (Xducer ID) to it. The technology has been around for 6 years but has not been added to the P66 until lst year. You can ID a P66 ID TM transducer by he label on the top of the unit. jpg?t=1325778538

What is ID TM.

Thanks to Airmar ....

Transducer ID™ is made possible by a small microcontroller that is embedded into each transducer. This microcontroller talks with the connected echosounder via a single conductor in the transducer cable. This feature enables the transducer to transmit important data to the echosounder, including transducer model, functions, frequency, power rating, beam pattern, impedance, ceramic element configuration and acoustic window material.

Through this Transducer ID™ feature the echosounder knows the precise frequency, operating power and impedance so it can “tune” its operation to optimize performance. This results in superior detection of fish targets, bottom composition and contour over a wide range of conditions. This information also helps protect the integrity of the system by preventing transducer overpowering.

All Airmar transducer that have this feature will carry this ID. Here's a picture of my TM 260 you can see the ID. 4.jpg?t=1328137329

Note: Some of the previous sonar models from current sonar manufacturers might not be compatible with this technology.


Mr T posted 06-04-2012 07:16 PM ET (US)     Profile for Mr T  Send Email to Mr T     
As always, some good news and some not so good news.

I got this reply from Airmar, very helpful and a timely response:

Good Day, I cannot comment on what may be causing the issue without testing the transducer or having screen shots of the problem, but it is possible to have delamination although it is a very rare occurrence. However, if you would like to use the P66 on the A65 we can certainly help you with that. The dealer was correct in that there is not a factory transducer made to connect directly into the unit, but we can supply you with an adapter cable and a P66 that will work just fine. The part number of the transducer is P66-Ray and the adapter is E66066 and everything will be plug and play. Best Regards,Sales DepartmentGEMECO Marine Accessories1141 Ron McNair Blvd

So that part is great news. I was taken aback though, to find that the adaptor cable, about 24 inches in length has a suggested MSRP of $125.00, which is about the cost of the transducer itself. So far I have found it as low as 65 dollars online.

I did ask the sale group to confirm if there are any differences between the two models for my peace of mind.

Mr T posted 06-04-2012 07:46 PM ET (US)     Profile for Mr T  Send Email to Mr T     
Bluewaterpirate, thanks for that information, I pulled the wiring diagrams for the both units and cannot find any reference to a line that performs that function, although the Rev of both wiring diagrams is in fact -01 indicating it is rather old.

Mr T posted 06-05-2012 12:09 PM ET (US)     Profile for Mr T  Send Email to Mr T     
Further update, I got this today from the sales group:

The P66 is different than the P58. The P66 has a higher quality depth element that uses noise filtering to help the returns while the P58 is more of an analog unit. The P66 also has a more efficient design compared to the P58 so it performs better at higher speeds. With that being said, the differences between the two are not substantially different but the P66 is an all around better unit.

To my mind, this is rather ambiguous, and does not clear it up very mich. oh well, I need to decide what to do at this point.

It is a 6 plus year unit, and I suppose I need to consider replacement...

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