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Author Topic:   Placement of Airmar P66 Transducer
jstarzy posted 09-09-2013 11:09 PM ET (US)   Profile for jstarzy   Send Email to jstarzy  
Hi all. I've completed troubleshooting of a Garmin 441s and Garmin transducer as written up in another thread. Based on that troubleshooting, I'll be mounting an Airmar P66 on the Montauk before next spring's launch.

Considering the popularity of the classic (1989) Montauk hull, can someone give me the optimal location for the P66 transom mount transducer from the keel with certainty?

I know Boston Whaler recommends the port side in their documentation, but Airmar told me to use the Starboard side. Airmar also provides a template for drilling that sets the Transducer height. I only need the distance from keel.

Anyone getting good results with a P66 and a classic Montauk hull? If so, can you please share your info?

Thanks to all-Jim.

jimh posted 09-12-2013 01:26 AM ET (US)     Profile for jimh  Send Email to jimh     
I recommend you follow the instructions from AIRMAR. The distance off centerline from the keel should probably be 12-inches or so.
jstarzy posted 05-18-2014 03:18 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Re opening this thread on the p66 transducer installation. I will be installing the unit at the end of the week. I'm still looking for distance from keel from anyone who has experience with successfully placing one on a classic Montauk transom. Airmar only sates at least 3" from the end of prop swing on the starboard side. I'll be mounting to a secured piece of starboard.

Considering the popularity of this hull and transducer, Can someone pass on a measurement from keel, away from strakes and air, that's performed well at all speeds up to 40mph?

Thanks so much--Jim.

jimh posted 05-19-2014 10:48 AM ET (US)     Profile for jimh  Send Email to jimh     
I recommend the approximate distance of 12-inches off keel centerline based on how the P66 has been working on my boat hull, which a P66 is mounted farther than 12-inches off center.

I find that the AIRMAR P66 transducer loses signal, probably from losing sufficient immersion into the water, if there is the slightest bit of heel or list on the boat toward Port side, that is, if the Starboard side of the boat raises ever so slightly out of the water. To correct for this, you can mount the transducer slightly lower than recommended, or, perhaps more appropriately, mount it closer to centerline, which will reduce this effect.

At the moment I have about 0.125-inch more depth of immersion possible with the range of adjustment in the mounting slots. If this does not help reduce the problem of signal loss when heeling to Port, then I will be moving the P66 closer to centerline.

jstarzy posted 05-19-2014 01:07 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Thanks Jim. I went through a long history of transducer mounting threads on continuous wave yesterday. It's interesting that the debate between port or starboard side mounting goes on and on without resolution. BW states port and transducer manufacturers state starboard.

Maybe Tom Clark has the best advice: either side will work?

My personal experience has been all on the starboard side, a P32 Airmar transducer with Apelco fish finder and a Garmin transducer with Garmin 400C fish finder. The Airmar/Apelco performed better than the Garmin. It was not perfect, though, as it frequently loss lock at speed.

The new set up will be a new Airmar P66 with a Garmin 441S combo sonar-chart plotter. I'm tempted to mount the king-starboard to the port side and try the P66 there as BW recommends. The propeller turbulence argument that the prop trails the transducer while underway keeping turbulence away from the transducer makes sense to me. However, why don't the transducer manufacturers consider this? Hmmmm?

So I will look under the classic, smirked, 17' hull for smooth bottom away from strakes as best I can with the boat on the trailer. I'll mount the king starboard and transducer on the port side as close to centerline but at least 3" away from the prop swing, and based on the make-up of the bottom of the hull for smoothness. The king starboard mounting plate will give me some flexibility for adjustment, if needed. I'll report back with more info after the sea trial. This case study can add to all the data already on the site.

Thanks so much.--Jim S.

Tom W Clark posted 05-19-2014 04:16 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I think jimh offers sound advice. If the diameter of the propeller is 14" maximum then the blade tip can be, at the most, 7" from the centerline of the keel. If Airmar recommends at least another 3" of clearance beyond that then that is 10"

If the transducer is 2" wide then the centerline of the transducer is another inch, so call it 11" as a minimum lateral distance from keel to centerline of transducer.

I just installed a transducer (not an Airmar P66) on a classic 1989 Montauk last Friday evening. This transducer had previously been mounted to port in a lousy position at the apex of the transom shape where the main hull meets the sponson. This position is high and tends to have air funneled to it making it unsuitable.

I moved the transducer to starboard and simply placed it about half way between the keel and the apex of the transom shape. I did not measure the lateral distance, but I suspect it is about 12" off-center of the keel.

The placement advice from Whaler dates back to the 1960s when depthsounder transducers were much larger and tended to act as mini-trim tabs. Since small outboard powered boats tend to list to port from propeller torque, adding a stern lifting force to port made sense to counteract this listing tendency.

With modern small transducers, I do not think it matters much and having it placed to starboard makes for cleaner rigging; the transducer cable can be neatly brought up the transom and bundled with other rigging running along the steering cable to the console.

jstarzy posted 05-20-2014 03:40 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Thanks Tom. Is there an owner-feedback on how last Friday's transducer installation is performing?

Tom and Jim and their logic have me back to mounting the P66 on the starboard side at about 12" from keel if the bottom of the boat at that distance is free of strakes and everything else. I'll report back after the sea trial.

Thanks--Jim S.

floater88 posted 05-27-2014 06:20 PM ET (US)     Profile for floater88  Send Email to floater88     
Just scored a free Airmar P66 ; its cable had been chewed through by rodents. Ordered a junction box and mount from Airmar. I'm planning on leaving the Lowrance transducer on the starboard side and mounting the Airmar on the Port side about 12-inches from the keel. I also have a kicker on the starboard side but the transducer will be mounted between both motors. I'm hoping I have no problems. I will post how it goes when I get the parts and get her done. Good luck with your placement.
jstarzy posted 06-01-2014 01:05 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Hi all....

I finished the installation last weekend and launched the Montauk on Friday. The Airmar P66 is mounted on a piece of King Starboard on the starboard side of the transom at 13.5 inches from center-line. There is a bend in the transom at around 11 inches from center-line and a strake in the bottom (at about 1/3 boat length back from the bow) at 12 inches from center-line, both prohibiting placement of the transducer at those points. The P66 is mounted without the included angle-shim and seems fairly parallel to the waterline without it. It is mounted 1/8" below the bottom of the boat on its left side. Everything is done as instructed by Airmar.

Unfortunately, the Garmin GPSMAP 441S loses lock (blinks at last value) consistently at each acceleration to and above 20 MPH and does not restore until speed is lowered. The Garmin unit is a new-refurb, sent as a replacement by Garmin and set to automatic for all sonar functions. I have the ability to move the P66 up and down by about an 1/8th inch without relocating the bracket. I can move the full bracket and P66 about a 1/2 inch to the left and about 2 inches to the right while still mounted to the King-Starboard.(But still difficult to move while the Montauk is in the water).

Any ideas on how to improve the performance? Also...If Jim H. can advise on how to link to a picture of the installation, I can post one if this would be helpful.

Thanks so much...

Jim S.

jimh posted 06-02-2014 01:06 AM ET (US)     Profile for jimh  Send Email to jimh     
With my AIRMAR P66 I am also seeing some loss of signal at speed. This was improved with deeper immersion. Try pushing the mount lower.

[If you don't have a public photo hosting website set up, just email me your digital image and I will include it here.]

Jefecinco posted 06-02-2014 09:11 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
If you've reached the bottom limit of your transducer mount try bumping the trailing edge of the transducer down a little before removing and remounting the transducer.

After installing the transducer on my former Dauntless 16 in accordance with Lowrance and Airmar recommendations I continued to lose bottom readings at higher speeds. The Lowrance employee I spoke with recommended tilting the transducer slightly more downward and it solved the problem.


jstarzy posted 06-02-2014 06:20 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Thanks guys.

Photo: AIRMAR P66 position on Boston Whaler MONTAUK transom
Photo of the transom with P66 attached on the King StarBoard

Thanks for the tips on angle and a lower position in the water. Coincidentally, Airmar is offering identical advice. There is one problem, though. The P66 does not have a continuously variable angle adjustment, it uses a shim (that I did not install) to achieve a greater angle off the transom. Airmar notes in the installation guide that no shim is needed for boats with 12 degree to 18 degree transom angle. Tom Clarke indicates in another post that a Classic 17 Montauk has a 17 degree transom angle. With this info and by seeing the trailing edge of the transducer pitched down just a bit, I chose not to use the shim. It seems this conflicts with the FAQ below.

I will attempt to lower the transducer first and test and then add the shim if needed if I can manage to do this while the Montauk is in low water in its slip.

Here is an excerpt from an Airmar FAQ I found today:

If you are still seeing poor performance at speed, this usually indicates that the transducer needs to be mounted lower so that more of the face of the transducer is in contact with the water at speed.
To make this adjustment, loosen the mounting screws, and slide the transducer 1/2" lower and re-test. You may need to re-drill holes. If you do so, be sure to seal the old holes with manufacturer approved, below the waterline caulking or epoxy.
You also may want to add another plastic wedge (supplied with the installation kit) so that when looking at the side of the transducer the back or stern of the transducer is noticeably lower than the bow or front of the transducer. This angle will not affect depth readings. Doing this adjustment will help keep the transducer in hard contact with the water at higher speeds.


Jim S.

jimh posted 06-02-2014 08:14 PM ET (US)     Profile for jimh  Send Email to jimh     
I like the position on the transom vis-a-vis its horizontal location. Try running it deeper.

On my install, the P66 is presently as far down as it can go on the original holes drilled from the template. It works well at speed until the boat heels to Port.

jstarzy posted 06-07-2014 09:07 AM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Hi all. Yesterday, Friday, I moved the P66 tranducer down as far as the bracket would allow, a drop of about a 1/2" as instructed in the Airmar FAQ. No improvement per a quick trial. With some help, I brought the transom of the Whaler to shore and mounted the shim behind the bracket as also instructed in the FAQ by Airmar bringing the rear of the unit farther into the water. No improvement. In fact, the unit is now struggling to re-establish lock once lost when reduced to slow or no speed. Incidentally, the fairly large P66 is acting like a trim tab and lifting the starboard side of the hull at speed.

With no adjustments left to go without re-drilling, I phoned Garmin Tech Support. Prior tech support from Garmin was superb as they were interested, informative and had made a complete replacement of the 441S last season when I explained the problem at that point. Today's GARMIN tech support (and I'm being kind) was ANYTHING BUT HELPFUL. The agent was APATHETIC. He listened to my story and said the transducer is becoming aerated and losing lock. He said I was fortunate that a P66 held any kind of lock above 12-13 MPH. He offered no other advice, recommendation or tips. Just live with it. I told him I'd be posting a summary of the call with GARMIN on a web forum and would phone Airmar next.

The Airmar agent was eager to hear my story and puzzled as to the performance of the system as the mounting of the unit seemed correct. He said the Garmin unit was not at fault as it was working properly at speeds below 20 MPH . He offered to discuss this with his colleagues and email or phone me back. I sent him the transom picture in this thread for reference.

He got back via email in about 2 hours with the following note that I've reduced to the most pertinent portions:

***Good afternoon Jim,

Thanks for the picture - great/clean install by the way.

That answers the initial questions I had regarding installation. It appears as though you have that transducer as far below the boundary layer as you can get.

You've obviously tried several locations at the current spot but you may want to move farther away from the center-line. There may be less turbulence / vibration.

As far as the system itself goes I doubt it is a performance issue with the sounder, or the package for that matter. You are getting good performance at idle speed up to 20mph. That means that as far as I can tell the system is working fine. The issues mostly arise when the boat reaches a certain speed at which point the transducer loses bottom. Although many transducers advertise they can read bottom at a wide range of speeds the truth is each boat is different.

You may want to look at page 2 of the owner's manual (attached) and consider raising the transducer so that the template is closer to the waterline. Or you could have the transducer tested to make sure it has the proper impedance.

Unfortunately I honestly cannot give you a definitive way to ensure that a P66 will hold depth at speeds 20mph and higher. Other P66 transducers have been able to hold depth and faster speeds so it is possible.

I will continue to check on this and have reached out to Boston Whaler to see if they have any further suggestions.

In the meantime if there is anything else I can do please let me know.


I'm pleased that Airmar responded so thoroughly but it seems there is really little advice other than another location more starboard, potentially in less turbulent water. I am also considering asking Airmar for a replacement P32, a smaller transducer that I had more luck with on a previous Apelco Fishfinder on this same boat. Even though mounting the transducer is always recommended as close to center-line as possible, by all manufacturers and members of this forum, the former P32 was mounted farther to starboard and as mentioned, I recollect it was more effective in holding speed lock at that position. The plugged holes from the P32 and former installation to that can be seen in the picture in this thread.

I'd be interested in any comments for improvement from others on the forum. This has become quite a puzzling project and case-study.

Jim S.

Basshole posted 06-08-2014 12:12 AM ET (US)     Profile for Basshole  Send Email to Basshole     
Jim, could you post a picture of your transom from the side? I would like to see the angle that the transducer sits relative to the transom. The dead rise angle is irrelevant to your install. I believe that when your boat gets up on plane and the bow flattens out you transducer is sending signals behind the boat instead of below it. Therefore, when these signals reflect off the bottom and return as "echoes" they are not being seen by the transducer and data is lost. It needs to be a low as possible but the trailing edge of the transducer may need to be even lower.

In order to get good readings the transducer needs to be relatively level with the waterline, not necessarily the boat itself, to see the echoes. This can be a bit of a challenge if the boat angle changes drastically when it goes from low speeds to planing and the bow comes down. I have seen people struggle with this placement using the Airmar TM260s which are meant for deep water use and shoot a very narrow cone angle below the boat. Having sold 3000 transducer mounts in 2.5 years, I have helped a lot of people install transducers on their boats. If I can't get it right, I have someone you can contact (even Airmar goes to him for advice) if we can't get this right.

Basshole posted 06-08-2014 12:17 AM ET (US)     Profile for Basshole  Send Email to Basshole     
I forgot to ask what size and weight is your motor? If you have a 115hp or a big four stroke, that may give us some clues because 17's sterns sit pretty low with that additional weight,
jimh posted 06-08-2014 09:04 AM ET (US)     Profile for jimh  Send Email to jimh     
Let us assume the boat is in water that is 100-feet deep. The sound from the transducer must travel 100-feet to the bottom, then return 100-feet to the surface. The speed of propagation of sound in water is given as roughly 1,497-meters/second, or 4,911-feet per second. The time necessary for the sound to travel 200-feet will thus be

1-second/4,911-feet x 200-feet = 0.04-seconds

Now we consider the boat is moving at a speed of 30-MPH. In 0.04-second the boat will advance

(30-miles/1-hour x 5280-feet/1-mile x 1-hour/3600-seconds) x 0.04-seconds = 1.76-feet

We know that the sound from the transducer is spreading in a cone. Even with a very narrow cone angle, say 10-degrees, after the sound has travelled 200-feet the cone will be covering a distance of

beam spread = 2 x tan(ConeAngle/2) x 200-feet
beam spread = 2 x tan(5) x 200-feet
beam spread = 35-feet

As long as the transducer is pointing straight down, it will be very unlikely the boat can outrun the return echoes, unless the boat is amazingly fast or the cone angle is as narrow as a laser beam. The instructions from AIRMAR clearly say:

For the best performance, the transducer beam must be aimed straight at the bottom.

When the P66 is installed on a transom without the added wedge, and the transom is on a typical Boston Whaler, the orientation of the P66 toward the bottom is going to be to aim a little bit forward of the boat, if anything, and not aim astern of the boat. With the typical trim on the boat when on plane, the bow is going to be higher than the static trim, so this will aim the sound even farther ahead of the boat.

I think the real source of the problem is loss of signal through turbulent and aerated water close to the transducer face. The bottom face of the transducer should be operating in clear, non-aerated, non-turbulent water.

I have given more information about the installation of the AIRMAR P66 on my boat in another article, and it may be of interest to readers, too:

The other article mentions this procedure, suggested by AIRMAR:

AIRMAR gives a valuable method to determine if the transducer is too high or too low. They suggest watching the echoes while making a turn to the left and right. If the transducer is mounted on Starboard, and you turn to the right, the Starboard side of the transom will lower into the water. If the SONAR echoes improve in a right turn, the transducer is mounted too high and should be lowered. If echoes improve in a left turn, the transducer is too low and should be raised. Using this method, I saw the echoes improve in right turns.

AIRMAR also notes in their FAQ that transom mount transducers can be the hardest to get working properly:

Transom mount transducers—while they are the easiest to install, can be the hardest to get working properly at speed. Fine adjustments are needed for good high speed performance.


Another article in the AIRMAR FAQ suggests the diagnostic technique of making a turn to the left or right and observing the echo signals:

...gradually increase speed while making moderate turns in both directions. Note, if the performance improves while the boat is turning toward the transducer side, the transducer is probably in aerated water or coming out of the water. You probably need to adjust the transducer's position.


Finally, that same article suggests:

If all else fails, move the transducer closer to the centerline of the boat. Repair unused screw holes.

In my installation that is about the point where I am now. I will likely have to move it closer to centerline. I will make one more test with the present location before giving up.

jstarzy posted 06-08-2014 09:51 AM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Hi Basshole(!) and Jim H....

Thank you both for your comments.

Basshole--it's a 2003 Yamaha 90HP 2S that weighs 263-lbs. A light motor for the 1989 Montauk.

I cannot send a picture of the side view. The boat is in the water for the season. I was fortunate to be able to work out the adjustments on Friday by jumping in the water at low tide for the minor adjustment down and beaching the transom with help for the addition of the angle shim. Incidentally, the shim is now making certain the trailing edge (back) of the P66 is definitely deeper in the water than the leading edge (front).

Considering the original installation position per the Airmar template placed the lowest portion of the transducer (port side)at 1/8" below the hull, moving it down Friday brings it to about 5/8" below the hull with the shim pointing the rear trailing edge down. Exactly as recommended in the Airmar FAQ.

Unless Basshole's or his suggested expert can offer advice, I'm left to try:

-- the C-clamp and 2x4 temporary testing technique of trial and error by moving the transducer around various points on the transom until something works better. I'm skeptical, however, as there is a lot of stuff in the way on a Montauk's transom that will interfere with clamping a board securely.

-- just moving the p66 more starboard where the P32 used to be (see plugged holes to starboard side of P66 in picture in this thread. This may not happen soon, though as the boat's in the water for the season

-- asking Airamr for a replacement, smaller P32 (limited to 200 kHz, though) that won't act as a trim tab like the large P66 does and will fit back in the original holes as long as I can back out the sealed stainless screws. This position seemed to perform better when I was using an Apelco with a P32.

-- nothing. Live with it per the apathetic advice from Friday's Garmin rep!

Thanks for your interest and comments guys...I'm all ears.

Jim S.

saumon posted 06-08-2014 10:38 AM ET (US)     Profile for saumon  Send Email to saumon     
For what it's worth, here's the same transducer on a different hull (a 1991 Outrage 17):

I never loose signal at any speed, but mine is screwed directly on the transom. Could it be, and it's totally a guess, that the piece of starboard isn't perfectly even with the hull bottom (maybe a bit higher), thus causing turbulence in front of the transducer?

jimh posted 06-08-2014 03:31 PM ET (US)     Profile for jimh  Send Email to jimh     
Saumon--many thanks for linking to your installation photo. I see you have the transducer on the Port side. If I end up moving my P66 closer to centerline, I will probably go to the Port side location, too. That will allow me to leave the Lowrance Skimmer where it sits now, on Starboard. Although the Port side is always described in the AIRMAR literature as less desirable, I really don't see how it makes much difference for an outboard engine installation where the propeller is two feet or more astern of the transducer. Wash from the propeller could never reach the transducer unless the boat were making sternway.
saumon posted 06-08-2014 04:35 PM ET (US)     Profile for saumon  Send Email to saumon     
Please note that my engine is mounted on a 4" setback bracket, which could also be a factor, placing the transducer farther from the propwash.
saumon posted 06-08-2014 07:30 PM ET (US)     Profile for saumon  Send Email to saumon     
I took some measurements: the center of the transducer bracket is 14 1/2" from the keel centerline. When installing, I focused more on finding a straight, even spot than actually being exactly at 12". On the vertical plane, when placing a straight edge along the bottom of the hull, the forward part of the transducer sit 1/4" lower while the trailing edge is 3/8" lower than the bottom.
Basshole posted 06-09-2014 04:05 AM ET (US)     Profile for Basshole  Send Email to Basshole     
jstarzy--If your transom angle is 17 degrees and the cone angle of your p66 is 11 degrees at 200kHz the echoes could be missing your transducer as they are reflected. Try installing the wedge and see what happens. I run my boat in very choppy water some times at high speeds if I am 60+ miles plus off the N. CA coast and I usually lose bottom when my bow is bouncing up and down. The stern isn't coming out of the water but the transducer must be pointing all over the place while this is happening I would imagine.

Also, looking at your bottom paint I noticed it's very rough and clefted. It has the appearance of slate tile almost. If the bottom of your boat looks like your transom then I would also suspect some turbulent water coming off the back of the boat which would likely get worse as your speed increases. Even small bumps can cause cavitation interference in the same way a thru-hull pick up or a strake can. The StarBoard block being too close to the bottom of the transom could also be the problem as already suggested. It it at least 1/4-inch above the bottom? A 1/2-inch above would be even better, hence why we chamfer the top edge of the Stern Saver to reduce the likelihood of water hitting the bottom corner of the block.

Also, West Marine sells the Garmin 441S without a transducer so you can choose from a variety of options. Did you "tell" your unit its got an Aimar p66 connected to it when you installed it? My Lowrance HDS units require me to select what transducers I am using so that the unit can properly calibrate itself to the transducer I selected off the menu.

Also, what frequency are you running at? It's a dual frequency transducer. Are you at 50-kHz (55 degree cone angle) or at 200-kHz (11 degree cone angle)? What depths are you at when losing signal? What are the water's surface conditions: big swells, tight chop, flat and glassy? What is the bottom contour: flat, sloped, variable? I think we just need some more info. This is not going to be solved by using JimH's "perfect world" assumptions. It's going to go beyond that, although his turbulent water theory is a possibility.

The more I think about it, I feel like it might have more to do with your settings on the Garmin unit rather than the transducer placement itself.

If all else fails give Gil Travis from Semper Fi Fishing a call at 1 (800) 925-0341 or email him at He knows more about this topic than anyone I know, even JimH, believe it or not! Tell him Scott from Stern Saver sent you. Actually, JimH should probably give him a call, too, so he can finally get his sounder working properly as well.

floater88 posted 06-09-2014 06:49 AM ET (US)     Profile for floater88  Send Email to floater88     
I also just finished my Airmar P66 install. I put mine on the port side between the two motors. This 1988 Revenge 20 WT is used for Salmon fishing and I primarily run the small kicker so according to Airmar the transducer is on the starboard side of my kicker:) This transducer had its cable chewed through by animals so that red round box you see is an Airmar Connection Box. Supposed to be waterproof and I sure hope it is. Will test this out when I put the boat in the water. As you can see in one pic I did use the wedge, and the transducer is pointed downwards towards the stern as per instructions. Its location is about 12 inches from the keel. I will post a follow up after I test it. Good luck with yours!

jimh posted 06-09-2014 01:00 PM ET (US)     Profile for jimh  Send Email to jimh     
ROGER on the transducer being on the Starboard side of the auxiliary engine. That is actually quite funny.

Let's hear from you after you test the installation to see how it works.

saumon posted 06-09-2014 01:30 PM ET (US)     Profile for saumon  Send Email to saumon     

could you please enlighten me on what is this clamped thing on your kicker's mid-section housing with what look like an air hose quick-connect?

floater88 posted 06-09-2014 04:51 PM ET (US)     Profile for floater88  Send Email to floater88     
That is an EZ Steer. There are two of those quick disconnects, one on either motor, and there is a telescoping rod that goes between them. It ties the kicker motor to the main so you can steer the little one with the big ones steering wheel. If you have a tilt function on your kicker the rod will lengthen or shorten when you tilt up or down. Works really well when you get the tension adjustments right.
saumon posted 06-09-2014 07:04 PM ET (US)     Profile for saumon  Send Email to saumon     
Thanks; I've seen the Panther-type that connect to the front bracket but never this one.
floater88 posted 06-10-2014 05:32 AM ET (US)     Profile for floater88  Send Email to floater88     
I've had both and they both work great. The Panther is way cheaper though.
floater88 posted 06-10-2014 12:40 PM ET (US)     Profile for floater88  Send Email to floater88     
Took the Revenge out for a fish this morning. At 1.6 mph you can see the Airmar P66 is working showing depth.

The next pic [was taken at a] speed of 40.6 mph and I still have bottom lock.

At all speeds, and even when getting up on plane, I never lost bottom lock. I configured the HDS Unit to recognize the Airmar and enabled the paddle wheel speed but it only worked sporadically. I will tinker with it some more and hope to get it working.

The only thing that concerns me is that junction box. That red lid is only press on. While under way,or sitting still, the bottom half of the box is in water. Airmar sais it's water proof but i don't trust it so i'm going to recheck all my connections and silicone that lid shut.

I unplugged the Airmar and plugged in the original Lowrance and it was evident the Airmar show more [arches] (fish) and a sharper presentation of the bottom. With a bit of fine tuning I will know when i'm over a hard or soft bottom. Hope all this helps in your install.
Hope this helps.

jimh posted 06-10-2014 07:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the images. I get similar results, without the wedge, until I turn to Port. I am fairly confident that having the transducer mounted closer to centerline is the key element of the installation.
jimh posted 06-10-2014 07:19 PM ET (US)     Profile for jimh  Send Email to jimh     
Re the AIRMAR junction box: give us a view of what's inside. I don't think too much is going on inside the box other than electrical connections. You might consider just making a good splice in the cable and covering it with heat-shrink tubing.
floater88 posted 06-10-2014 08:35 PM ET (US)     Profile for floater88  Send Email to floater88     
I looked at just doing a splice and it wasn't recommended due to the two bare wires inside the bundle of 14 wires. I took the cover off the box just now and there was water in there but it didn't seem to affect the head unit. I'm gonna seal it with silicone just to be sure.

jstarzy posted 06-11-2014 10:21 AM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Hi guys. Interesting discussion, but anymore tips on the subject of the thread and my P66/441S system?

Tom Clark--you've been helpful in the past. Any ideas? Much appreciated.--Jim S.

floater88 posted 06-11-2014 12:33 PM ET (US)     Profile for floater88  Send Email to floater88     
Sorry to highjack your thread but I though my work might help yours. Have you tried moving it a little closer to the keel? Looks like you got an inch or two of room to move it away from the 'step' in the hull to the left of your mount?
jimh posted 06-30-2014 09:37 AM ET (US)     Profile for jimh  Send Email to jimh     
Update on my P66 transducer placement: I have removed the P66 from the transom.

I spent a few days on the boat and had the cables for both the Lowrance Skimmer and the Airmar P66 available at the back of my HDS-8, so I could quickly switch them. We found some deep water, about 590-feet, in Lake Michigan. I compared the two transducers. They both seemed to give good echoes from 590-feet.

To switch the transducers, I was setting the HDS SONAR to STOP. I figured this stopped the high-power pulse to the transducer from the head unit. I was then disconnecting one cable and connecting the other, but not shutting off the power to the HDS. I did this a few times. Then I happened to read the warning label on the Airmar cable. It warns specifically to not connect the transducer to a sounder when the power is on due to a risk of damage to the speed sensor circuit. Oops. I was fortunate. I did not damage the speed sensor circuit in the P66, and I stopped hot-switching the cables.

The P66 worked worse at any boat speed than I had recalled. Perhaps the boat was always heeling the wrong direction--we were running with some cross winds all the time, and that tends to make the boat heel. The performance at speed was just not very good. I decided the P66 in its current mounting location was not usable.

When we got back from the cruise I pulled the P66 off the transom. My next move will be to try mounting it on the Port side, with about a 12-inch offset from centerline. Before I do that, I have to patch up the three holes in the transom from the P66. My transom is begining to look like it had measles and scratched them--there are a lot of scars from old transducer mounting locations. Most of them are from the gear that was onboard from a prior owner. The three P66 holes are my first contribution to new and now unused holes. I am giving some thought to adding a piece of KING StarBoard or similar material to the transom before the next attempt to mount the P66. If I don't hit a good location on this next attempt, I will give up on transom mounting the P66. Maybe I can turn it into a tow-fish mount--it has a nice long cable.

floater88 posted 07-05-2014 11:04 AM ET (US)     Profile for floater88  Send Email to floater88     
I too made the mistake of hot switching the two transducers and in my case It looks like I did damage the speed circuit. I found that the Airmar P66 actualy did work better than the lowrance as I got more fish hooks and bait balls using it then not. When I marked fish I made a waypoint and switched transducers and went over the spot again and the P66 showed more than the Lowrance. Unfortunately it looks like that Junction box isn't too water proof afterall. I sealed it with silicone caulking but i still got way to much interference on the screen as compared to the Lowrance. I will leave the transducer mount where it is for now and when I buy a new one I can just use that mount. Good luck with yours.
jstarzy posted 07-18-2014 10:00 PM ET (US)     Profile for jstarzy  Send Email to jstarzy     
Hi all. Here's some more information on the installation of an AIRMAR P66 on the transom of a classic Boston Whaler MONTAUK 17, the initial boat discussed in this thread.

I had the Montauk out last Friday. The Airmar P66 and Garmin 441S are now working the poorest they have since the original installation this Spring. The P66 is mounted with the angle shim and is well submersed into the water. Depth readings are not acquired at the dock in 3 to 4 feet of water. I have to reboot the unit in at least 6 feet of water to get a reading at all. Once sending a valid reading and then I exceed 20 mph, lock is lost and the reading blinks. If I slow the boat down under 20 MPH all the way to idling with no movement in clear, non-aerated water, the unit does not re-establish lock, it continues to blink and will not get a reading until I reboot the Garmin. Once rebooted, the system repeats the same problematic cycle.

I'm extremely disappointed with this equipment. I can understand loss of lock in aerated water and am willing to try relocating the P66 again, but not re-establishing lock after returning to no forward movement in non aerated water is very frustrating and puzzling and seems to indicate a defect with either the NEW P66 or NEW 441S.


jimh posted 07-18-2014 10:28 PM ET (US)     Profile for jimh  Send Email to jimh     
Here is an update on the placement of the AIRMAR P66 transducer on my boat, a Boston Whaler REVENGE 22 W-T Whaler Drive: I spent an hour today filling in the old mounting holes where the AIRMAR P66 was mounted on the transom with epoxy resin to restore a waterproof seal. My next step will be to extract the cable of the AIRMAR P66 from the boat so I can remove the transducer completely. At this time I do not have plans to install it on the transom in the immediate future. I may experiment with it at some later date. The Lowrance Skimmer transducer is working so much better that I have decided I don't really need the P66 for my boating needs this season.
Marko888 posted 07-23-2014 01:28 AM ET (US)     Profile for Marko888    
I just installed an Airmar P66 on my Outrage 18. It is centred at 11" to starboard from the keel, and mounted exactly as per the included instructions. It and my Furuno 1670F hold bottom at 40mph in freshwater.
jimh posted 07-23-2014 08:37 AM ET (US)     Profile for jimh  Send Email to jimh     
The reports of good results with the AIRMAR P66 transducer are encouraging. Like all SONAR transducers, the performance depends on the location. Mounting close to keel centerline on a v-hull boat seems imperative.
jimh posted 07-26-2014 05:15 AM ET (US)     Profile for jimh  Send Email to jimh     
Airmar P66 mounted on transom of Boston Whaler OUTRAGE 22
Airmar P66 mounted on transom of Outrage 22

Jack H. writes:

"I have been following the recent thread on the placement of the Airmar P66 transducer. As seen in the picture [above], my P66 is mounted on the port side about 12-inches from the keel centerline and performs very well at any speed with my Lowrance HDS 7 Gen2."

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