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Old 24-04-2018, 19:43   #1
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Depth transducer location

I'm installing a new depth transducer on a used boat. It did not have a through-hull transducer before. So, where should I locate it?

There's no perfectly flat section of the bottom, so I can favor the bow or port or starboard. In each location the sensor will cant either toward the front or toward either side. The port and starboard areas are flatter than the bow. So, none of them are ideal.

The other option would be to build up a flange that could support the transducer toward a more vertical installation. The disadvantage is having the sensor protrude into the water flow.
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Old 24-04-2018, 19:53   #2
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Re: Depth transducer location

FYI, I've already purchased a Raymarine product Part Number: M78713-PZ-A
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Old 24-04-2018, 22:50   #3
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Re: Depth transducer location

Quote:
Originally Posted by Bigjim View Post
FYI, I've already purchased a Raymarine product Part Number: M78713-PZ-A
The pointing of the transducer to port or starboard I think is called the deadrise angle. Looks like that part number is a Airmar P319 which has a max dead rise of 8 degrees. Probably wants to be flat in the fwd/aft plane.

HTH

Al

Link : http://www.airmar.com/uploads/Brochures/p319.pdf
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Old 24-04-2018, 23:11   #4
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Re: Depth transducer location

I've always put my transducer in front of the keel, on the center line fore and aft. A little G10 donut, ground out to fit your hull shape, and epoxied on, will make it face forward slightly, pointing in front of the keel, rather than to the side. Seems to work for me. Haven't hit the bottom yet. You won't notice a difference in speed any more than no transducer at all.
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Old 25-04-2018, 06:27   #5
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Re: Depth transducer location

Quote:
Originally Posted by Bigjim View Post
I'm installing a new depth transducer on a used boat. It did not have a through-hull transducer before. So, where should I locate it?

There's no perfectly flat section of the bottom, so I can favor the bow or port or starboard. In each location the sensor will cant either toward the front or toward either side. The port and starboard areas are flatter than the bow. So, none of them are ideal.

The other option would be to build up a flange that could support the transducer toward a more vertical installation. The disadvantage is having the sensor protrude into the water flow.
The question I have is why go with a thru-hull installation at all? Assuming your hull is solid glass you could easily shoot through the hull. The transducer can installed in an end cap of a short length of PVC pipe cut to an angle to match the deadrise of the hull and epoxied to the hull. Fill that with mineral oil, screw on the cap and you're done with no holes in the hull, No?

FWIW...
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Old 25-04-2018, 06:30   #6
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Re: Depth transducer location

Quote:
Originally Posted by Souzag818 View Post
I've always put my transducer in front of the keel, on the center line fore and aft. A little G10 donut, ground out to fit your hull shape, and epoxied on, will make it face forward slightly, pointing in front of the keel, rather than to the side. Seems to work for me. Haven't hit the bottom yet. You won't notice a difference in speed any more than no transducer at all.
My boat came from the factory with this setup and works fine although I have hit the bottom a few times.
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Old 25-04-2018, 07:24   #7
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Re: Depth transducer location

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Originally Posted by svHyLyte View Post
The question I have is why go with a thru-hull installation at all? Assuming your hull is solid glass you could easily shoot through the hull. The transducer can installed in an end cap of a short length of PVC pipe cut to an angle to match the deadrise of the hull and epoxied to the hull. Fill that with mineral oil, screw on the cap and you're done with no holes in the hull, No?

FWIW...
Cool idea. I have not heard of that before. The transducer I bought is designed as a through hull. I think the boat had an old internal one, but it doesn't work any more. It's probably 20 years old. Do you know any instructions on how to do that online?
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Old 26-04-2018, 05:50   #8
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Re: Depth transducer location

Jim--

One can find representative instructions at Stow Marine or simply do a web search on "Internally mounted depth transducer". The photo below is representative of an internal oil bath mount. Just a length of PVC pipe epoxied to the hull with a threaded end cap.




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Old 26-04-2018, 08:06   #9
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Re: Depth transducer location

Excellent. Thanks. Does the device work as well this way in your experience?
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Old 26-04-2018, 18:22   #10
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Re: Depth transducer location

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Excellent. Thanks. Does the device work as well this way in your experience?
One might loose a little "absolute depth" in deeper water. For a sailing yacht however, so long as the depth reported is accurate to 50-100 feet you're good. (That depth is based upon using the 5 and/or 10 fathom curves as a means of laying off but paralleling a coast or shore line although with all the "wizard" electronics these daze, the "old" but tried and reliable practices are not much know to, or followed by, the current generation of sailing aficionados, much to their disability when their wizard electronics "butt out"!).

N'any case, good luck.
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Old 30-04-2018, 06:27   #11
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Re: Depth transducer location

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Originally Posted by BigAl.NZ View Post
The pointing of the transducer to port or starboard I think is called the deadrise angle. Looks like that part number is a Airmar P319 which has a max dead rise of 8 degrees. Probably wants to be flat in the fwd/aft plane.

HTH

Al

Link : http://www.airmar.com/uploads/Brochures/p319.pdf
It's actually a P19.
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Old 04-05-2018, 10:02   #12
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Re: Depth transducer location

A technician at my boatyard said that the in-hull installation is mostly used for high-powered transducers, used by fishermen. He recommends drilling a hole and installing it thru-hull. The one I purchased is a low-power Airmar model.

Anyone have any opinions about that?
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Old 04-05-2018, 10:20   #13
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Re: Depth transducer location

Your transducer is 375 Watts. Hardly low power. It's at the upper range of what you will find for a standard depth sounder. Power gets higher for fish finders 600+ Watts.

The Airmar P79S is only 100 Watts (50 Watts for NMEA 0183) and it's an In-Hull transducer.

As mentioned above you are going to lose considerable depth readings but it will accurately read 50+ feet which is more than you need to know for keeping off the bottom.

If you have a goal of knowing for certain that you are in 100+ feet of water than you should go thru-hull or step up to a higher power In-Hull transducer that will require a sounder module or fish finder.

Tell me what your exact goal is and I will tell you the cheapest options.
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Old 04-05-2018, 13:04   #14
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Re: Depth transducer location

The model I bought was the P319. According to the following data it provides 600 Watts.

http://www.airmartechnology.com/uplo..._hull%20LR.pdf

All I care about is knowing whether the water is 20 feet or less. I draw 5.5 feet so I'm pretty safe in most parts of Lake Michigan, but when we enter a new harbor, we need know what's happening under the keel. I'm just going by what this tech said.

Obviously, if I drill a hole, I can't un-drill it. (Yes, we can patch it.) But if I build in in-hull installation, little harm is done. I can always drill a hole later.
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Old 04-05-2018, 14:09   #15
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Re: Depth transducer location

Quote:
Originally Posted by Bigjim View Post
FYI, I've already purchased a Raymarine product Part Number: M78713-PZ-A
Quote:
Originally Posted by KeelMe View Post
It's actually a P19.
As I already said, the M78713-PZ-A is a P19 not a P319. The P19 is a depth transducer(or old school fish finder) the P319 is a fish finder transducer.

Internally mounting the transducer you have as mentioned above will accurately fulfill your needs.
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