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post #1 of 16 Old 05-10-2008 Thread Starter
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Sonar transducer question...

So I'm looking into putting a combo fishfinder/gps unit in the boat; not looking to spend more than 400-500 bucks. I've seen a few about that I'm interested in, one or two of the Humminbirds and Lowrance's, Garmin has one or two that might be right for me.

The real question is, I need to mount the sonar transducer somewhere in the boat. There already is a humminbird depthfinder installed and working, it is connected to a little black thingie that is stuck to the inside of the hull, about halfway from the back and a little bit up the inside of the starboard side. What are the odds that I can I plug the cord from the black thingie into my new (not bought yet) unit. That being said, if it doesn't work...how much success has anyone had with inside the hull mounted transducers? The units I have been looking at are the "dual frequency" models, if that means anything.

Anyway, let me know what you think and I'll check in later.

Marty

1972 Bristol 26, "River Cabana"
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post #2 of 16 Old 05-10-2008
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Martsmth-

There have been quite a few threads on mounting a transducer internally without cutting a hole in the hull. Be aware that it won't work if the hull is cored.

Also, be aware that you probably won't be able to plug and play the new unit to the older transducer.

BTW, you may lose some discrimination and detail by shooting through the hull.

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post #3 of 16 Old 05-10-2008 Thread Starter
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Any idea if a 1972 bristol 26 is a "cored hull"? btw...what is a "cored hull"?
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I doubt a 1972 Bristol 26 is a cored hull. A cored hull is not made up of solid fiberglass but has a core material between two fiberglass skins. The core is often made of foam, like Airex which is used in Southern Cross boats, Divinylcell, which is used in some race boats—like Giulietta, or end-grain Balsa, which was used in many varied boats. The core material absorbs the sound and causes the transducer to fail to work properly.

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post #5 of 16 Old 05-10-2008
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Hello,

I have installed two Lowrance GPS / Sonar units, both with the transducer mounted inside the boat. The first transducer was epoxied to the hull, the second is held wit toilet bowl wax. Both work great and I haven't been able to find any loss of signal. I don't use mine for fishing, only to see the bottom.

Note that if you have two transducers on the same frequency, the displays of both may show 'weird' results. My boat has an old Datamarine depthfinder that works fine. If my Lowrance SONAR is set to dual frequency (50 and 200 hz) the Datamarine will show the current depth, then a real shallow number, then a real deep number, then the current depth. When I set the Lowrance to 200 hz, the Datamarine works normally.

Good luck,

Barry

Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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post #6 of 16 Old 05-10-2008 Thread Starter
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Hey Barry, care to comment on the particular Lowrance units you decided to go with, and a few details on installation of the transducer?
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post #7 of 16 Old 05-11-2008
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No fillers......

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Originally Posted by martsmth View Post
Any idea if a 1972 bristol 26 is a "cored hull"? btw...what is a "cored hull"?
Definitely not cored.
Bristol 26
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post #8 of 16 Old 05-11-2008
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Personally, I wouldn't spend over $100 on a depth-finder. They all do the same thing. Some with more bells and whistles than others.
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post #9 of 16 Old 05-11-2008
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are you looking for a true sonar or just a bottom display, there is a great difference, and requires much more thought, what might be your reason for this sonar / fish finder.

Brake Free
Lake Ontario
42 CC Passage
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post #10 of 16 Old 05-11-2008 Thread Starter
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artfuldodger,

my real reason for this fishfinder/sonar is to augment my current depthfinder (only a digital readout of actual depth) with a fishfinder....Here on the Hudson river, we get a really great run of striped bass. The bass tend to follow schools of herring, as well as school themselves...also, they tend to congregate in certain spots with structure. My thoughts are that I could get a fishfinder to help me find herring and stripers, as well as the depths/structures they tend to hang out in. Also, another "depthfinder" that will quell suspicions when I don't trust my true depthfinder....those are my reasons I suppose.

That stated....any reason why an inside the hull transducer wouldn't work out?

I also had another idea........call me crazy......


My bristol has a lazarette in the back where the outboard engine sits, there is an opening in the transom to allow for the outboard to function. The lazarette compartment is sealed from the rest of the boat obviously. Can I drill a hole in the bottom of the lazarette (through the hull and into the river) and install a through hull transducer, as long as I put the hole more than a foot from the lower unit of the outboard?

I envision a certain amount of water pouring through the hole, then stopping, me screwing the thing in, then pumping the water out. There naturally is an inch or two of water sloshing around in there all the time anyway, with barely enough freeboard at the transom (4-6 inches or so) to mount my 15 hp mercury.....

Would I sink my boat doing this? lol

I'll check back in after dinner.
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